Method and apparatus for performing direct communication with at least one other user equipment

ABSTRACT

A method and an apparatus for performing direct communication with at least one other user equipment are provided. The method and apparatus comprises upon generation of an event requiring the direct communication, transmitting a floor request, monitoring whether a response to the floor request is received from at least one adjacent UE, if a response to the floor request is not received until the floor request is transmitted a predetermined number of times at a predetermined interval, determining that a transmission right for the direct communication is granted, and if it is determined that the transmission right is granted, transmitting a signal to the at least one other UE by the direct communication.

PRIORITY

This application is a Continuation of U.S. patent application Ser. No.15/752,113, which was filed with the U.S. Patent and Trademark Office onFeb. 12, 2018, as a U.S. National Phase entry of InternationalApplication No. PCT/KR2016/008946, filed on Aug. 12, 2016, and claimspriority to U.S. Provisional Patent Application Nos. 62/204,171,62/235,873, 62/238,333, 62/241,856, 62/258,809, 62/275,541, and62/279,339, filed on Aug. 12, 2015, Oct. 1, 2015, Oct. 7, 2015, Oct. 15,2015, Nov. 23, 2015, Jan. 6, 2016, and Jan. 15, 2016, respectively, thecontent of each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates schemes for floor control with mediaburst control protocol for device to device communication.

2. Description of the Related Art

A floor control message is disclosed. Floor control in a conferencecall, push to talk makes a lot of sense. A number of people arediscussing a subject and politely ask for the floor each time theybelieve that they have something to say. Once they get an indicationthat the floor is available, they start to talk. A protocol candidate tobe used for floor control are the Binary Floor Control Protocol (BFCP)specified in request for comment (RFC) 4582 (An update of RFC 4582 isongoing in internet engineering task force (IETF) at the moment) andMedia Burst Control Protocol (MBCP) specified in open mobile alliance(OMA) Push to Communicate for Public Safety (PCPS).

3rd generation partnership project (3GPP) has started studying to evolveexisting networks to LTE (long term evolution)-based public safetysolutions, which name is Public Safety LTE (PS-LTE). Public safetynetwork provides communications for public safety services such aspolice, fire, ambulance, war, natural disaster, and so on. In general,public safety network is mainly used for mission criticaltext/voice/video communications among large number of users.

Mission Critical Push to Talk (MCPTT) service in PS-LTE is intended tosupport one-to-one and one-to-many voice/video communications, whereeach user has the ability to gain an access to the permission to talk inan arbitrated manner. That is, MCPTT is a walkie-talkie-like service andthe user can gain the permission to talk by pressing the ‘talk button’to start talking. Push-to-talk sessions are basically half-duplexcommunications: while one user speaks, the others should listen. Somefloor control functionalities are required for controlling the talkpermission.

In off-network case, the multicast manner is used as efficientcommunication way for floor control unlike in the on-network. Inaddition to the feature, a current speaking MCPTT client acts as a floorarbitrator like floor control server in on-network environment. Thisindicates that floor control manner is server-less without dedicatedcentral server. For this reason, the floor control for off-networkrequires that the floor arbitrator is delegated to next talker when thecurrent speaking MCPTT client completes speaking and another MCPTTclient is waiting for floor. So, a good protocol to be used for floorcontrol of off-network may satisfy these features.

MBCP is tailor made for mission critical applications and is focusing onallowing a participant to talk immediately. The use of real time controlprotocol (RTCP) allows the “floor control” session to be negotiated inthe same speed as the media. No extra message for establishing a floorcontrol session is needed. Further, including floor status message(taken, idle, etc.) in media is very convenient when media isbroadcasted. BFCP is focusing on floor control for conferenceapplications. The use of acknowledgement for each and every message inthe unreliable mode also when media is broadcasted is not suitable.

SUMMARY

For the reasons above it is proposed to select MBCP as the base for thefloor control protocol. However, MBCP is server-based floor controlprotocol and can't fully support the floor control on device to devicecommunication. So, this invention proposes Server-less floor controlsupporting the resolution of race condition and floor arbitratordelegation.

According to an embodiment of the present disclosure, a method performedby a user equipment (UE) is provided, with the method includingreceiving, from an other UE included in a group call in which the UE isincluded, a first message for requesting permission for transmission;identifying that the permission for transmission is granted to the otherUE in case that the UE does not transmit, to the other UE, a secondmessage in response to the first message repeatedly transmitted, and theUE receives, from the other UE, a third message indicating that thepermission for transmission is granted to the other UE; and receivingmedia data from the other UE.

According to another embodiment of the present disclosure, a userequipment (UE) is provided that includes a transceiver and a controllerconfigured to receive, via the transceiver, from an other UE included ina group call in which the UE is included, a first message for requestingpermission for transmission, identify that the permission fortransmission is granted to the other UE in case that the UE does nottransmit, via the transceiver, to the other UE, a second message inresponse to the first message repeatedly transmitted and the UEreceives, via the transceiver, from the other UE, a third messageindicating that the permission for transmission is granted to the otherUE, and receive, via the transceiver, media data from the other UE.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a message flow of requesting permission with grantedmessage.

FIG. 2 shows a message flow of requesting permission without grantedmessage.

FIG. 3 show a flow of auto resolution for request collision on localgranted mode with granted message.

FIG. 4 show a flow of auto resolution for request collision on localgranted mode without granted message.

FIG. 5 shows a flow of manual resolution for request collision on localgranted mode.

FIG. 6 shows a flow of auto resolution for request collision on normalgranted mode with granted message.

FIG. 7 shows a flow of auto resolution for request collision on normalgranted mode without granted message.

FIG. 8 shows a flow of manual resolution for request collision on normalgranted mode.

FIG. 9 shows a flow for requesting permission during speech.

FIG. 10 shows a floor participant state diagram.

FIG. 11 shows a floor participant state diagram (enhanced operation).

FIG. 12 shows a floor participant state diagram with release state.

FIG. 13 shows a floor participant state diagram with release and queuestate.

FIG. 14 shows a floor participant state diagram (queuing operation ofautomatic way).

FIG. 15 shows a floor participant state diagram (queuing operation ofmanual way).

FIG. 16 shows a floor participant state diagram (basic operation).

FIG. 17 shows a floor participant state diagram (basic operation).

FIG. 18 shows an APP message format.

FIG. 19 shows a floor request message format.

FIG. 20 shows a floor granted message format.

FIG. 21 shows a floor taken message format.

FIG. 22 shows a floor deny message format.

FIG. 23 shows a floor release message format.

FIG. 24 shows a floor request queue status message format.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope of the invention. Inaddition, descriptions of well-known functions and constructions may beomitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

A floor control protocol is based on RTCP Application Packets (RTCP:APP), as defined in IETF RFC 3550 and may use ports negotiated at aSession establishment. The RTCP uses the next highest odd port of evenport of real-time transport protocol (RTP), as default value.

A MCPTT Client for off-network supports at least one of following basicMedia Burst Control Protocol messages, MBCP Media Burst Request, MBCPMedia Burst Granted, MBCP Media Burst Deny, and MBCP Media BurstRelease. The MBCP Media Burst Request is used by the MCPTT Client torequest permission from the other client to send a Media Burst. The MBCPMedia Burst Granted is used by the MCPTT Client to notify the MCPTTClient that it has been granted permission to send a Media Burst. TheMBCP Media Burst Granted message includes information about a stoptalking timer. The MBCP Media Burst Deny is used by the MCPTT Clientwith permission to send media to notify a MCPTT Client sending floorrequest message that it has been denied permission to send a MediaBurst. The MBCP Media Burst Release is used by the MCPTT Client tonotify the other MCPTT Clients that it has completed sending a MediaBurst or it cancels the permission before sending the Media Burst or itrequests the MCPTT Client with permission to send media to cancel thequeued Media Burst request when queuing is supported by the MCPTTClients.

A MCPTT Client performing supporting queuing of MBCP Media Burst Requestmessages support the following additional Media Burst Control Protocolmessages, MBCP Media Burst Queue Status Request, and MBCP Media BurstQueue Status.

The MBCP Media Burst Queue Status Request is used by the MCPTT Client toget information about the MCPTT Client's position in the floor requestqueue. The MBCP Media Burst Queue Status is used by the MCPTT Clientwith permission to send media to notify the MCPTT Client that the MBCPMedia Burst Request has been queued.

TABLE 1 Floor control message MBCP Floor request: used to request afloor for Media Burst Request message media transfer Floor granted: usedto indicate that a Media Burst Granted message request for floor isgranted and media transfer is possible. Floor taken: used to indicatethe floor Media Burst Taken message is given to another MCPTT user.Floor rejected: used to indicate that a Media Burst Deny message requestfor the floor is rejected. Floor release: used to indicate the MediaBurst Release message media transfer is completed and floor is released.Request queue position: used to request Media Burst Queue Status thequeue position about the floor Request requesting UE. Queue position:used to indicate the Media Burst Queue Status floor request is queuedand the queue position to the floor requesting UE.

Message flows are disclosed.

Requesting permission during silence is disclosed.

FIG. 1 shows a message flow of requesting permission with grantedmessage.

Once a group call session is established and when the floor is idle anyuser can request floor. The flow below shows how a MCPTT client requeststhe floor, is granted the floor and how media is distributed to otherMCPTT clients in the group call session.

The procedure can be two modes of operation according to Granted mode asa result of session establishment: A Local Granted mode and NormalGranted mode. Two modes are needed to receive granted message forpermission to talk.

Steps of the flow for the Local Granted mode are explained by referringto FIG. 1 (101).

A user of a MCPTT client A 100 presses the PTT button (102).

The MCPTT client A 100 sends a Media Burst Request message (103), andindicates to the user to start to talk (104).

The MCPTT client A 100 may send a MBCP Media Burst Taken messagesinstead of the Media Burst Request messages 103. The MBCP Media BurstRequest message 103 and the MBCP Media Burst Taken message may includePriority level, Random number for collision resolution of floorrequests.

When receiving the request message, a MCPTT client B 200, MCPTT client C300, and MCPTT client D 400 may prepare receiving RTP media.

The MCPTT client A 100 sends the RTP media to MCPTT clients B 200, C300, and D 400 (105). The MCPTT clients B 200, C 300, and D 400 receivethe RTP media.

The MCPTT client C 300 sends a Media Burst Granted message 106 whenreceiving the request message 103.

When receiving the floor request message 103, all MCPTT clients 200,300, 400 may perform the backoff mechanism to avoid sending the samefloor grant messages in response to the multicast-based floor requestmessage 103. In the backoff mechanism, the MCPTT clients randomly choosethe backoff value in the range [0, maxBackoff] for sending the floorgrant message 106. That is, clients 200, 300, 400 may defer theirtransmission for the chosen backoff time period. Eventually, one ofMCPTT clients, choosing the smallest number, firstly sends the floorgrant message. If MCPTT clients receive the floor grant message which issent from other MCPTT client, then the MCPTT clients may not send thefloor grant message in order to prevent the feedback message implosions.

Steps of the flow when Local Granted mode is not used are explained byreferring to FIG. 1 (107).

A user of a MCPTT client A 100 presses the PTT button (108).

The MCPTT client A 100 sends a Media Burst Request message (109).

The MCPTT client A 100 may send a MBCP Media Burst Taken messagesinstead of the Media Burst Request messages 109. The MBCP Media BurstRequest message 109 and the MBCP Media Burst Taken messages may includePriority level, Random number for collision resolution of floorrequests.

A MCPTT client C 300 sends a Media Burst Granted message 110 whenreceiving the request message 109.

When receiving the floor request message 109, all MCPTT clients 200,300, 400 may perform the backoff mechanism to avoid sending the samefloor grant messages in response to the multicast-based floor requestmessage 109. In the backoff mechanism, the MCPTT clients randomly choosethe backoff value in the range [0, maxBackoff] for sending the floorgrant message 110. One of MCPTT clients, choosing the smallest number,firstly sends the floor grant message. If MCPTT clients receive thefloor grant message which is sent from other MCPTT client, then theMCPTT clients may not send the floor grant message.

In case of on-network, a MBCP server may send a Media Burst Takenmessage indicating “taken” to MCPTT client B 200, C 300, and D 400 foracknowledgement. But it is unnecessary to send the Media Burst Takenmessage as the MCPTT client can already know the ‘Listening’ status asreceiving the Media Burst Granted message indicating ‘Talking’ viamulticast communication.

When the Media Burst Granted message is received, the MCPTT client A 100may send RTP media (112). The MCPTT clients B, C and D receive the RTPmedia.

Requesting permission without granted message is disclosed. FIG. 2 showsa message flow of requesting permission without granted message.

Once group call session is established and when the floor is idle, anyuser can request floor. The flow below shows how a MCPTT client requeststhe floor, how the floor is granted, and how media is distributed toother MCPTT clients in the group call session.

The procedure can be two modes of operation according to Granted mode asa result of session establishment: A Local Granted mode and NormalGranted mode. Two modes are needed to wait a certain time (i.e., keyperformance indicator (KPI): MCPTT Access Time) instead of receivinggranted message for permission to talk.

A user of a MCPTT client A 100 presses the PTT button (202).

The MCPTT client A 100 may send a Media Burst Request message (203).

The MCPTT client A 100 may send a MBCP Media Burst Taken messagesinstead of the Media Burst Request messages 203. The MBCP Media BurstRequest message 203 and the MBCP Media Burst Taken message may includePriority level, Random number for collision resolution of floorrequests.

After a T timer is expired (204), the MCPTT client A 100 may send RTPmedia (205) if the MCPTT client A doesn't receive a MBCP Media BurstRequest messages from other MCPTT clients. The MCPTT clients B 200, C300, and D 400 receive the RTP media.

Auto resolution for request collision on local granted mode with grantedmessage is disclosed.

FIG. 3 show a flow of auto resolution for request collision on localgranted mode with granted message.

Once a group call session is established and when the floor is idle, anyuser can request floor.

FIG. 3 shows how a MCPTT client requests the floor, how the floor isgranted, and how media is distributed to other MCPTT clients in thegroup call session.

When two or more MCPTT clients request the floor simultaneously,collision may occur since MCPTT clients cannot detect and avoid otherMCPTT client's floor request messages.

MCPTT client A 100 and D 400 may send MBCP Media Burst Request messages303 a, 303 c simultaneously to the same group. The MBCP Media BurstRequest message 303 a, 303 c may contain at least one of a Prioritylevels (will be specified below) and a Random number (e.g.,synchronization source (SSRC) of RTP/RTCP).

The MCPTT client A 100 and D 400 may send MBCP Media Burst Takenmessages instead of the MBCP Media Burst Request messages. The MBCPMedia Burst Taken messages may include Priority level, Random number.

The MCPTT client A 100 and D 400 may send RTP media (303 b, 303 d)without receiving MBCP Media Burst Granted message.

When receiving the MBCP Media Burst Request messages, all MCPTT clientsmay buffer the received MBCP Media Burst Requests 303 a, 303 c and checkwhether or not another MBCP Media Burst Requests are transmitted for acertain time (i.e., transmitting time of the messages to the servicecoverage).

When receiving the MBCP Media Burst Request messages, the MCPTT clientsB 200 and C 300 may receive the RTP media 303 b, 303 d.

When the two or more Floor requests 303 a, 303 c are transmittedsimultaneously, the receiving MCPTT clients may perform the operation ofselecting a next talker based on the priority level and the randomnumber. The MCPTT client (i.e., the next talker) may be chosen withhigher priority in the MBCP Media Burst Requests. If the priority issame, then the MCPTT client with the higher Random number (e.g. SSRC ofRTP/RTCP) may be chosen as the next talker.

The MCPTT client C 300 may send a Floor Grant message 304 afterselecting the talker.

When receiving the floor request message 303 a or 303 d, all MCPTTclients may perform the backoff mechanism to avoid sending the samefloor grant messages in response to the multicast-based floor requestmessage 303 a or 303 c. In the backoff mechanism, the MCPTT clientsrandomly choose the backoff value in the range [0, maxBackoff] forsending the floor grant message 304. That is, the clients may defertheir transmission for the chosen backoff time period. Eventually, oneof MCPTT clients, choosing the smallest number, firstly sends the floorgrant message 304. If MCPTT clients receive the floor grant message 304which is sent from other MCPTT client, then the MCPTT clients may notsend the floor grant message in order to prevent the feedback messageimplosions.

When the Media Burst Granted message 304 is received, the MCPTT client A100 may revoke the floor (305).

The MCPTT client A 100 stops sending RTP media and receives RTP media(306).

For the procedure above, users of the MCPTT clients can automaticallyresolve the request collision without pressing the PTT button again.

Auto resolution for request collision on local granted mode withoutgranted message is disclosed.

FIG. 4 shows a flow of auto resolution for request collision on localgranted mode without granted message.

Once a group call session is established and when the floor is idle, anyuser can request floor.

FIG. 4 shows how a MCPTT client requests the floor, how the floor isgranted, and how media is distributed to other MCPTT clients in thegroup call session.

When two or more MCPTT clients request the floor simultaneously,collision may occur since MCPTT clients cannot detect and avoid otherMCPTT client's floor request messages.

MCPTT client A 100 and D 400 may send MBCP Media Burst Request messages303 a, 303 c simultaneously to the same group. The MBCP Media BurstRequest message 303 a, 303 c may contain at least one of a Prioritylevel (will be specified below) and a Random number (e.g.

SSRC of RTP/RTCP).

The MCPTT client A 100 and D 400 may send the MBCP Media Burst Takenmessages instead of the MBCP Media Burst Request messages. The MBCPMedia Burst Taken messages may include Priority level, Random number.

The MCPTT client A 100 and D 400 may send RTP media (403 b, 403 d)without receiving MBCP Media Burst Granted message. When receiving theMBCP Media Burst Request messages, the MCPTT clients B 200 and C 300receive the RTP media.

When the two or more Floor requests 403 a, 403 c are transmittedsimultaneously, the receiving MCPTT clients may perform the operation ofselecting a next talker based on the priority level and the randomnumber. After the T timer is expired, the MCPTT client A 100 and D 400choose the next talker with higher priority in the MBCP Media BurstRequests. If the priority is same, then the MCPTT client with the higherRandom number (e.g. SSRC of RTP/RTCP) may be chosen as the next talker.In this case, The MCPTT client D 400 may be chosen as the next talker.

The MCPTT client A 100 may revoke the floor (405).

The MCPTT client A 100 stops sending RTP media and receives RTP media(406).

For the procedure above, users of the MCPTT clients can automaticallyresolve the request collision without pressing the PTT button again.

Manual resolution for request collision on local granted mode isdisclosed.

FIG. 5 shows a flow of Manual resolution for request collision on localgranted mode.

Once a group call session is established and when the floor is idle, anyuser can request floor. FIG. 5 shows how a MCPTT client requests thefloor, is granted the floor and how media is distributed to other MCPTTclients in the group call session.

When two or more MCPTT clients request the floor simultaneously,collision occurs since MCPTT clients cannot detect and avoid other MCPTTclient's floor request messages.

MCPTT client A 100 and D 400 may send MBCP Media Burst Request messages503 a, 503 c simultaneously to the same group. The MBCP Media BurstRequest message 503 a, 503 c may contain a Priority level (will bespecified below).

The MCPTT client A 100 and D 400 may send MBCP Media Burst Takenmessages instead of the MBCP Media Burst Request messages. The MBCPMedia Burst Taken messages may contain a Priority level.

The MCPTT client A 100 and D 400 may send RTP media without receivingMBCP Media Burst Granted message.

When receiving the MBCP Media Burst Requests 503 a, 503 c, all MCPTTclients may buffer the received MBCP Media Burst Requests 503 a, 503 cand check whether or not another MBCP Media Burst Requests aretransmitted for a certain time (i.e., transmitting time of the messagesto the service coverage).

When receiving the MBCP Media Burst Request messages 503 a, 503 c, theMCPTT clients B 200 and C 300 may receive the RTP media.

When the two or more Floor requests 503 a, 503 c are transmittedsimultaneously, receiving MCPTT client A 100 and D 400 may perform theoperation of notification 504 a, 504 b (e.g. beep or message) ofcollision and send the MBCP Media Burst Request messages by releasingPTT button 505 a, 505 b. If the MCPTT client can use the priority levelin floor request messages, it chooses highest priority of client as nexttalker. The user may be notified of the collision condition as a beep ormessage if it is not highest priority.

The MCPTT client A 100 may send the MBCP Media Burst Request messages tothe same group by pressing PTT button again (505 a).

When receiving the MBCP Media Burst Requests, all MCPTT clients maybuffer the received MBCP Media Burst Requests and check whether or notanother MBCP Media Burst Requests are transmitted for a certain time.

The MCPTT client C 300 may send Floor Grant message 509 after selectingthe talker.

When receiving the floor request message, all MCPTT clients may performthe backoff mechanism to avoid sending the same floor grant messages inresponse to the multicast-based floor request message. In the backoffmechanism, the MCPTT clients randomly choose the backoff value in therange [0, maxBackoff] for sending the floor grant message. That is, theclients may defer their transmission for the chosen backoff time period.Eventually, one of MCPTT clients, choosing the smallest number, firstlysends the floor grant message. If MCPTT clients receive the floor grantmessage to be sent from other MCPTT client, then the MCPTT clients maynot send the floor grant message in order to prevent the feedbackmessage implosions Auto resolution for request collision on normalgranted mode with granted message is disclosed.

FIG. 6 shows a flow of auto resolution for request collision on normalgranted mode with granted message.

Once a group call session is established and when the floor is idle, anyuser can request floor. FIG. 6 shows how a MCPTT client requests thefloor, how the floor is granted, and how media is distributed to otherMCPTT clients in the group call session.

When two or more MCPTT clients request the floor simultaneously,collision may occur since MCPTT clients cannot detect and avoid otherMCPTT client's floor request messages.

MCPTT client A 100 and D 400 may send MBCP Media Burst Request messages603 a, 603 b simultaneously to the same group. The MBCP Media BurstRequest messages 603 a, 603 b may contain at least one of a Prioritylevel (will be specified below) and a Random number (e.g. SSRC ofRTP/RTCP).

The MCPTT client A 100 and D 400 may send MBCP Media Burst Takenmessages instead of the MBCP Media Burst Request messages. The MBCPMedia Burst Taken messages may include Priority level, Random number.

When receiving the MBCP Media Burst Requests, all MCPTT clients maybuffer the received MBCP Media Burst Requests and check whether or notanother MBCP Media Burst Requests are transmitted for a certain time(i.e., transmitting time of the messages to the service coverage).

When the two or more Floor requests 603 a, 603 b are transmittedsimultaneously, receiving MCPTT clients may perform the operation ofselecting a next talker based on the priority level and random number.The MCPTT client (i.e., the next talker) may be chosen with higherpriority in the MBCP Media Burst Requests. If the priority is same, thenthe MCPTT client with the higher Random number (e.g. SSRC of RTP/RTCP)may be chosen as the next talker.

Referring to FIG. 6, in operation 601, a group call session isestablished between the MCPTT clients A 100, B 200, C 300, and D 400.Local Grant mode was not negotiated when the group call was established.In operations 602 a and 602 b, the MCPTT clients A 100 and D 400 detectthat a user presses PTT button respectively.

In operations 603 a and 603 b, the MCPTT clients A 100 and D 400 sendthe MBCP Media Burst Request messages simultaneously to the same group.The message contains a Priority level and a Random number (e.g. SSRC ofRTP/RTCP) The MCPTT clients A 100 and D 400 can send the MBCP MediaBurst Taken messages instead of Request messages. The MBCP Media BurstTaken messages may include a Priority level, and a Random number.

When receiving the MBCP Media Burst Requests, all MCPTT clients maybuffer the received the MBCP Media Burst Requests and check whether ornot another MBCP Media Burst Requests are transmitted for a certain time(i.e., transmitting time of the messages to the service coverage).

When the two or more Floor requests are transmitted simultaneously, thereceiving MCPTT clients perform the operation of selecting next talkerbased on the priority level and random number. The MCPTT client ischosen with higher priority in the MBCP Media Burst Requests. If thepriority is same, then the MCPTT client A 100 with the higher Randomnumber (e.g. SSRC of RTP/RTCP) is chosen as the next talker.

In operation 604, the MCPTT client C 300 sends the Floor Grant messageafter selecting the talker.

When receiving the floor request message, all MCPTT clients perform thebackoff mechanism to avoid sending the same floor grant messages inresponse to the multicast-based floor request message. In the backoffmechanism, the MCPTT clients randomly choose the backoff value in therange [0, maxBackoff] for sending the floor grant message. That is, theclients may defer their transmission for the chosen backoff time period.Eventually, one of MCPTT clients, choosing the smallest number, firstlysends the floor grant message. If MCPTT clients receive the floor grantmessage to be sent from other MCPTT client, then the MCPTT clients donot send the floor grant message in order to prevent the feedbackmessage implosions

When the Media Burst Granted message is received, in operations 605 and606, the MCPTT client A 100 may start to talk indication and send RTPmedia.

The MCPTT clients B, C and D receive the RTP media.

For the procedure above users can automatically resolve the requestcollision without pressing PTT button again.

Auto resolution for request collision on normal granted mode withoutgranted message is disclosed.

Once a group call session is established and when the floor is idle anyuser can request floor.

FIG. 7 shows how a MCPTT client requests the floor, is granted the floorand how media is distributed to other MCPTT clients in the group callsession.

When two or more MCPTT clients request the floor simultaneously,collision occurs since MCPTT clients cannot detect and avoid other MCPTTclient's floor request messages.

Referring to FIG. 7, in operation 701, a group call session isestablished between the MCPTT clients A 100, B 200, C 300, and D 400.Local Grant mode was not negotiated when the group call was established.In operations 702 a and 702 b, the MCPTT clients A 100 and D 400 detectthat a user presses PTT button respectively.

In operation 703 (including 703 a and 703 b), the MCPTT clients A 100and D 400 send the MBCP Media Burst Request messages simultaneously tothe same group. The message may contain the following: PrioritylevelRandom number (e.g. SSRC of RTP/RTCP) The MCPTT clients A 100 and D400 can send the MBCP Media Burst Taken messages instead of Requestmessages. The MBCP Media Burst Taken messages may include Prioritylevel, Random number. The MCPTT clients A 100 and D 400 can wait for amax buffering time T. (where, T<the key performance indicator) When thetwo or more Floor requests are transmitted simultaneously, the receivingMCPTT clients perform the operation of selecting next talker based onthe priority level and random number. After the T timer is expired, theMCPTT clients A 100 and D 400 choose the next talker with higherpriority in the MBCP Media Burst Requests. If the priority is same, thenthe MCPTT client with the higher Random number (e.g. SSRC of RTP/RTCP)is chosen as the next talker. In this case, in operation 705 a, theMCPTT client A is chosen as the next talker and may start to talkindication (a beep).

In operation 406, the MCPTT client A sends RTP media. The MCPTT clientsB, C and D receive the RTP media.

For the procedure of FIG. 7, users can automatically resolve the requestcollision without pressing PTT button again.

Manual resolution for request collision on normal granted mode isdisclosed.

Once a group call session is established and when the floor is idle anyuser can request floor.

FIG. 8 shows how a MCPTT client requests the floor, is granted the floorand how media is distributed to other MCPTT clients in the group callsession.

When two or more MCPTT clients request the floor simultaneously,collision occurs since MCPTT clients cannot detect and avoid other MCPTTclient's floor request messages.

Referring to FIG. 8, in operation 801, a group call session isestablished between the MCPTT clients A 100, B 200, C 300, and D 400.Local Grant mode was not negotiated when the group call was established.In operations 802 a and 802 b, the MCPTT clients A 100 and D 400 detectthat a user presses PTT button respectively.

In operation 803 (including 803 a and 803 b) the MCPTT clients A 100 andD 400 send the MBCP Media Burst Request messages simultaneously to thesame group. The message may contain the following information elementPriority level

The MCPTT clients A 100 and D 400 can send the MBCP Media Burst Takenmessages instead of Request messages. The MBCP Media Burst Takenmessages may contain Priority level.

When receiving the MBCP Media Burst Requests, all MCPTT clients maybuffer the received the MBCP Media Burst Requests and check whether ornot another MBCP Media Burst Requests are transmitted for a certain time(i.e., transmitting time of the messages to the service coverage).

When the two or more Floor requests are transmitted simultaneously, thereceiving MCPTT clients A 100 and D 400 perform the operation ofnotification (e.g. beep or message) of collision in operations 804 a and804 b and send the MBCP Media Burst Request messages in operations 806and 807 by releasing PTT button by its user in operations 805 a and 805b. If the MCPTT client 100 or 400 can use the priority level in floorrequest messages, it chooses highest priority of client as next talker.The user must be notified of the collision condition as a beep ormessage if it is not highest priority.

MCPTT client A 100 sends the MBCP Media Burst Request messages to thesame group by pressing PTT button again.

When receiving the MBCP Media Burst Requests, all MCPTT clients maybuffer the received the MBCP Media Burst Requests and check whether ornot another MBCP Media Burst Requests are transmitted for a certaintime.

In operation 809, the MCPTT client C 300 sends the Floor Grant messageafter selecting the talker.

When receiving the floor request message, all MCPTT clients perform thebackoff mechanism to avoid sending the same floor grant messages inresponse to the multicast-based floor request message. In the backoffmechanism, the MCPTT clients randomly choose the backoff value in therange [0, maxBackoff] for sending the floor grant message. That is, theclients may defer their transmission for the chosen backoff time period.Eventually, one of MCPTT clients, choosing the smallest number, firstlysends the floor grant message. If MCPTT clients receive the floor grantmessage to be sent from other MCPTT client, then the MCPTT clients donot send the floor grant message in order to prevent the feedbackmessage implosions

When the Media Burst Granted message is received, in operations 810 and811, the MCPTT client A may start to talk indication and send RTP media.

The MCPTT clients B, C and D receive the RTP media.

Requesting permission during speech is disclosed.

Once a group call session is established and when the floor is taken anyuser can request floor.

FIG. 9 shows how a MCPTT client requests the floor, is granted the floorand how media is distributed to other MCPTT clients in the group callsession.

Referring to FIG. 9, in operation 901, a group call session isestablished between 1 and N participants. The N participants may includethe MBCP clients A 100, B 200, C 300, and D 400.

And the MBCP client A 100 starts to talk.

Operation 902 (including 902 a, 902 b, 902 c, and 902 d) is performedduring speech of the MBCP client A 100.

In operation 902 a, the MBCP client A sends RTP media and in operation902 b, the user at the MBCP client B 200 presses the PTT button duringthe speech of MCPTT client A 100.

In operation 902 c, the MBCP client B 200 sends the MBCP Media BurstRequest message with the pre-emption priority.

In operation 902 d, the MBCP client A 100 revokes locally when receivingthe MBCP Media Burst Request message. If the priority of the MBCP clientA 100 is same as the MBCP client B 200, the MCPTT client A 100 may sendthe MBCP Media Burst deny message.

In operation 903, the MBCP client A 100 sends the MBCP Media BurstGranted message with Queue list indicating MBCP clients waiting for nextfloor. The Queue list includes set of priority, queue position, userIDof MBCP clients requesting to get permission to talk.

In operation 905, the MBCP client B 200 starts to talk indication andsends the RTP media. The MBCP clients A, C and D receive the RTP media.

Floor control procedures are disclosed.

The floor participant may support the state diagram and the followingstate transitions.

FIG. 10 shows the floor participant state diagram.

Referring to FIG. 10, if an RTP media packet or a floor control messagearrives in a state where there is no specific procedure specified forthe RTP media or the received floor control message, the floorparticipant may discard the floor control message or the RTP mediapacket and may remain in the current state. A badly formatted RTP packetor floor control message received in any state is ignored by the floorparticipant and does not cause any change of the current state.

An operation in the state “Start-stop” 1016 is described.

In this state no state machine exists.

In the state “Start-stop” 1016, the MCPTT call may be established by anoriginating MCPTT user.

When a MCPTT call is established with session announcement including anexplicit floor request, in operation 1020, the originating floorparticipants may create an instance of a floor participant statetransition diagram for basic operation state machine, and send FloorTaken message towards other floor participants, and enter the ‘O: haspermission’ state 1025.

In the state “Start-stop” 1016, the MCPTT call may be established by aterminating MCPTT user.

When a MCPTT call is established, in operation 1014, the terminatingfloor participant may create an instance of a floor participant statetransition diagram for basic operation state machine, and enter the ‘O:silence’ state 1017.

An operation in the state: ‘O: silence’ 1017 is described.

In this state a none of the MCPTT clients in the session is acting as afloor control server.

If the floor participant receives an indication from the MCPTT user tosend media in the state: ‘O: silence’ 1017, in operation 1006, the floorparticipant may send the Floor Request message (PTT button pressed) toother floor participants, and enter ‘O: pending request’ state 1027.

Upon receiving RTP media packets (R: RTP media) in the state: ‘O:silence’ 1017, in operation 1007, the floor participant may provide afloor taken notification to the MCPTT user, and enter ‘O: has nopermission’ state 1008.

Upon receiving Floor Taken message (R: Floor Taken) in the state: ‘O:silence’ 1017, in operation 1007, the floor participant may provide afloor taken notification to the MCPTT user, and enter ‘O: has nopermission’ state 1008.

An operation in the state: ‘O: has no permission’ 1008 is described.

In this state another MCPTT client does not have permission to sendmedia.

If the floor participant receives an indication from the MCPTT user tosend media in the state: ‘O: has no permission’ 1008, in operation 1003,the floor participant may send the Floor Request message (PTT buttonpressed) to other floor participants, and enter ‘O: pending request’state 1027.

When a Floor Release message is received (R: Floor Release) in thestate: ‘O: has no permission’ 1008, in operation 1012, the floorparticipant may instruct the MCPTT client to stop receiving RTP mediapackets, enter ‘O: silence’ state 1017, and, provide floor idlenotification to the MCPTT user.

When a Floor Granted message is received (R: Floor Granted) in thestate: ‘O: has no permission’ 1008 (i.e. when a Floor Request is pendingin the queue or a higher priority request is pending), in operation1026, the floor participant may instruct the MCPTT client to stopreceiving RTP media packets, if any, if the User ID in the floor grantmessage matches its own User ID, enter the state ‘O: has permission’1025, remain in ‘O: has no permission’ state, if the User ID in thefloor grant message don't match its own User ID, and update the queuestatus and notify the MCPTT user, Upon receiving RTP media packets (R:RTP media) in the state: ‘O: has no permission’ 1008, in operation 1005,the floor participant may instruct the MCPTT client to render the RTPmedia packets, and remain in ‘O: has no permission’ state 1008.

Upon receiving an indication from the MCPTT user to release the pendingrequest for the floor in the state: ‘O: has no permission’ 1008, inoperation 1005, the floor participant may send a Floor Release message(PTT button released) towards other floor participants, and remain in‘O: has no permission’ state 1008.

On firing of T13 (No RTP Media) timer in the state: ‘O: has nopermission’ 1008, in operation 1012, the PoC Client may instruct theMCPTT client to stop receiving RTP media, enter ‘O: silence’ state 1017,and, provide floor idle notification to the MCPTT user.

An operation in the state: ‘O: has permission’ 1025 is described.

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

Upon receiving encoded media from the MCPTT user or if encoded media isalready buffered in the state: ‘O: has permission’ 1025, in operation1021, the floor participant may instruct the MCPTT client to startsending RTP media packets (S: RTP Media) towards other MCPTT clients.The RTP media packet may include, media packets and payload attributesas defined in IETF RFC 3550, And the floor participant may remain in the‘O: has permission’ state 1025.

Upon receiving a Floor Release message (R: Floor Release) in the state:‘O: has permission’ 1025, in operation 1021, the floor participant mayremove the sender of the Floor Release message from the queue, if theUser ID in the floor release message matches the queued request of UserID, and, remain in the ‘O: has permission’ state 1025.

When a Floor Request message is received (R: Floor Request) in a sessionwhere queuing mode is not used in the state: ‘O: has permission’ 1025,in operation 1021, the floor participant may send the Floor Deny messageincluding reason field toward the other floor participants, and remainin the ‘O: has permission’ state 1025.

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher in thestate: ‘O: has permission’ 1025, in operation 1021, the floorparticipant may store the received Floor Request messages, send theFloor Request Queue Status message. The Floor Request Queue Statusmessage may be populated by indicating the User ID of the MCPTT clientin the floor request queue, indicating the SSRC of the MCPTT client inthe floor request queue, indicating the position of the MCPTT client inthe floor request queue, and indicating the priority level of the MCPTTclient in the in the floor request queue. And the floor participant mayremain in the ‘O: has permission’ state 1025.

Upon receiving an indication from the MCPTT user to release permissionto send RTP media in the state: ‘O: has permission’ 1025, in operation1022, the floor participant may send a Floor Release message (PTT buttonreleased) towards other floor participants, if no queued requests exist.The Floor Release message may be populated by including the sequencenumber of the last RTP media packet that was sent, if at least 1 RTPMedia packet was sent. The floor participant is expected to provide thesequence number in all cases when the floor participant knows thesequence number of the RTP media packets may set the sequence numberignore field to 1, if no RTP media were sent or if the floor participantis not capable of providing the correct sequence number. And the floorparticipant may enter the ‘O: silence’ state 1017.

When no more encoded media is received from the MCPTT user and if atleast one Floor Request message is stored in the state: ‘O: haspermission’ 1025 (i.e. queuing mode is used in the session), inoperation 1024, the floor participant may instruct the MCPTT client tostop sending RTP media packets towards other MCPTT clients, and send theFloor Granted message (PTT button released) toward the other floorparticipant. The Floor Granted message may be populated by indicatingthe User ID of the MCPTT client in the floor request queue, indicatingthe SSRC of the MCPTT client in the floor request queue, indicating theposition of the MCPTT client in the floor request queue, and indicatingthe priority level of the MCPTT client in the in the floor requestqueue. And the floor participant may enter the ‘O: pending granted’state 1023.

When a Floor Request message is received with a pre-emption priority (R:Floor Request with pre-emption) in the state: ‘O: has permission’ 1025,in operation 1024, the floor participant may instruct the MCPTT clientto stop sending RTP media packets towards other MCPTT clients, and senda Floor Granted message.

If floor control queuing mode is used in the session, the Floor Grantedmessage may be populated by indicating the User ID of the MCPTT clientin the floor request queue, indicating the SSRC of the MCPTT client inthe floor request queue, indicating the position of the MCPTT client inthe floor request queue, and indicating the priority level of the MCPTTclient in the in the floor request queue. And the floor participant mayenter the ‘O: pending granted’ state 1023.

An operation in the state: ‘O: pending request’ 1027 is described.

In this state the MCPTT client is waiting for a response to a Floorrequest message. The timer Txx (waiting time for collision detection ofrequests) is running in this state.

Upon receiving RTP media packets (R: RTP media) in the state: ‘O:pending request’ 1027, in operation 1002, the floor participant mayinstruct the MCPTT client to render the RTP media packets, and remain in‘O: pending request’ state 1027.

Upon receiving Floor Request Queue Status message (R: Floor RequestQueue Statue) in the state: ‘O: pending request’ 1027, in operation1004, the floor participant may update the queue status, if the User IDin the Floor Request Queue Status message matches its own User ID,notify the MCPTT user about the queue position, stop the timer Txx(waiting time for collision detection of requests); and enter ‘O: has nopermission’ state 1008.

Upon receiving Floor Deny message matching the MCPTT client own User ID(R: Floor Deny) in the state: ‘O: pending request’ 1027, in operation1004, the floor participant may stop the timer Txx (waiting time forcollision detection of requests), if the User ID in the Floor Denymessage matches its own User ID, and enter ‘O: has no permission’ state1008.

When the MCPTT client is receiving RTP Media and if Txx timer is firedin the state: ‘O: pending request’ 1027, in operation 1004, the floorparticipant may enter ‘O: has no permission’ state 1008, and providefloor idle notification to the MCPTT user.

When an indication from the MCPTT user to release the pending requestfor the floor is received and if RTP media is received (PTT buttonreleased and receiving media) in the state: ‘O: pending request’ 1027,in operation 1004, the floor participant may send a Floor Releasemessage towards other floor participants, stop the timer Txx (waitingtime for collision detection of requests), and enter ‘O: has nopermission’ state 1008.

When an indication from the MCPTT user to release the pending requestfor the floor is received and if no RTP media is received in the state:‘O: pending request’ 1027, in operation 1011, the floor participant maysend a Floor Release message (PTT button released) towards other floorparticipants, stop the timer Txx (waiting time for collision detectionof requests), and enter ‘O: silence’ state 1017.

If no RTP media is received until expiry of timer Txx in the state: ‘O:pending request’ 1027, in operation 1019, the floor participant may sendFloor Taken message towards other floor participants, and enter ‘O: haspermission’ state 1025.

Upon receiving Floor Granted message (R: Floor Granted) in the state:‘O: pending request’ 1027, in operation 1019, the floor participant maystop the timer Txx (waiting time for collision detection of requests),if the User ID in the Floor Granted message matches its own User ID, andenter ‘O: has permission state’ 1025.

An operation in the state: ‘O: pending granted’ 1023 is described.

In this state the MCPTT client is waiting for another client to takeover the role of Floor controller. The Timer T20 (No RTP Media) isrunning in this state.

Upon receiving the RTP media in the state: ‘O: pending granted’ 1023, inoperation 1018 the floor participant may request the MCPTT client tostart receiving RTP media packets, and enter ‘O: has no permission’state 1008.

On expiry of T20 (Granted re-send) timer in the state: ‘O: pendinggranted’ 1023, in operation 1021, the floor participant may enter ‘O:silence’ state 1017.

An operation in the state: Any state 1009 is described.

This state relates to the actions to be taken in all states defined forthe basic state diagram with the exception of the ‘Start-stop’ state1016 and the ‘Releasing’ state 1013.

Upon receiving a MCPTT call release step 1 request from the applicationand signaling plane when the MCPTT call is going to be released or whenthe floor participant is leaving the MCPTT call in the state: Any state1009, in operation 1010, the floor participant may stop sending floorcontrol messages other floor participants, request to the MCPTT clientto stop sending and receiving RTP media packets, and enter the‘Releasing’ state 1013.

An operation in the state: ‘Releasing’ 1013 is described.

The floor participant uses this state while waiting for the applicationand signaling plane to finalize the disconnection of a MCPTT call.

Upon receiving a MCPTT call release step 2 request from the applicationand signaling in the state: ‘Releasing’ 1013, in operation 1015 thefloor participant may release all resources including any running timersassociated with the MCPTT call, and enter the ‘Start-stop’ state 1016and terminate the ‘Floor control state machine —basic’ Hereinafter, Adetailed method of floor control procedures with timer for enhancingreliability will be described.

The floor participant may support the state diagram and the statetransitions specified in this subclause.

FIG. 10 illustrates the floor participant state diagram.

FIG. 11 illustrates the floor participant state diagram —enhancedoperation. State details are explained in the following subclauses.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant may discard thefloor control message or the RTP media packet and may remain in thecurrent state.

It is noted that a badly formatted RTP packet or a floor control messagereceived in any state is ignored by the floor participant and does notcause any change of the current state.

Hereinafter, referring to the FIG. 11, enhanced operations in connectionwith the floor participant state diagram will be described in detail.

As to a state of “Start-stop” (1114)

In this state no state machine exists.

In the FIG. 11, an operation for MCPTT call established —originatingMCPTT user (1117) is performed as follows:

When a MCPTT call is established with session announcement including anexplicit floor request, the originating floor participant: may create aninstance of a floor participant state transition diagram for basicoperation state machine; and

may send Floor Taken message towards other floor participants; and

may enter the ‘O: has permission’ state (1125).

In the FIG. 11, an operation for MCPTT call established —terminatingMCPTT user (1112) is performed as follows:

When a MCPTT call is established the terminating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine; and

may enter the ‘O: silence’ state (1115).

AS to a state of ‘O: silence’ (1115)

In this state a none of the MCPTT clients in the session is acting as afloor control server.

In the FIG. 11, an operation for sending floor request message (PTTbutton pressed) (1106) is performed as follows:

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may send the Floor Request message to other floor participants; and

may enter ‘O: pending request’ state (1103).

In the FIG. 11, an operation for receiving RTP media (R: RTP media)(1109) is performed as follows:

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media);

may request the MCPTT client to start rendering received RTP mediapackets; and,

may enter ‘O: has no permission’ state (1110).

In the FIG. 11, an operation for receiving a floor taken message (R:Floor Taken) (1109) is performed as follows:

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media); and,

may enter ‘O: has no permission’ state (1110).

As to a state of ‘O: has no permission’ (1110)

In this state another floor participant does not have permission to sendmedia.

In the FIG. 11, an operation for sending a floor request message (PTTbutton pressed) (1102) is performed as follows:

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

may send the Floor Request message to other clients; and,

may enter ‘O: pending request’ state (1101).

In the FIG. 11, an operation for receiving a floor release message (R:Floor Release) (1113) is performed as follow:

When a Floor Release message is received, the floor participant:

1. may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter ‘O: silence’ state (1115); and,

may provide floor idle notification to the MCPTT user.

In the FIG. 11, an operation for T13 (No RTP Media) timer fired (1113)is performed as follows:

On firing of T13 (No RTP Media) timer, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may enter ‘O: silence’ state (1115); and,

may provide floor idle notification to the MCPTT user.

In the FIG. 11, an operation for receiving a floor granted message (R:Floor Granted) (1105) is performed as follows:

When a Floor Granted message is received (i.e. when a Floor Request ispending in the queue or a higher priority request is pending), the floorparticipant:

may request the MCPTT client to stop rendering received RTP mediapackets, if any, if the User ID in the floor grant message matches itsown User ID;

may stop timer T13 (No RTP Media);

may enter the state ‘O: has permission’ (1125).

may remain in ‘O: has no permission’ state (1110), if the User ID in thefloor grant message don't match its own User ID; and,

may update the queue status and notify the MCPTT user;

In the FIG. 11, an operation for receiving RTP media (R: RTP media)(1105) is performed as follows:

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may restart timer T13 (No RTP Media); and,

may remain in ‘O: has no permission’ state (1110).

In the FIG. 11, an operation for sending a floor release message (PTTbutton released) is performed as follows:

Upon receiving an indication from the MCPTT user to release the pendingrequest for the floor, the floor participant:

may send a Floor Release message towards other floor participants; and,

may remain in ‘O: has no permission’ state (1110).

As to a state of ‘O: has permission’ (1125)

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

In the FIG. 11, an operation for sending RTP Media packets (S: RTPMedia) (1121) is performed as follows:

Upon receiving encoded media from the user or if encoded media isalready buffered the floor participant:

may request the MCPTT client to start sending RTP media packets towardsother MCPTT clients; and,

may remain in the ‘O: has permission’ state (1125).

In the FIG. 11, an operation for receiving a floor release message (R:Floor Release) (1121) is performed as follows:

Upon receiving a Floor Release message, the floor participant:

may remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and,

may remain in the ‘O: has permission’ state (1125).

In the FIG. 11, an operation for receiving a floor request (R: FloorRequest) (1121) is performed as follows:

When a Floor Request message is received in a session where queuing modeis not used, the floor participant:

may send the Floor Deny message including reason field toward the otherfloor participants; and,

may remain in the ‘O: has permission’ state (1125).

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher, thefloor participant:

may store the received Floor Request messages;

may send the Floor Request Queue Status message. The Floor Request QueueStatus message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may remain in the ‘O: has permission’ state (1125).

In the FIG. 11, an operation for sending a floor release message (PTTbutton released with no pending request in queue) (1122) is performed asfollows:

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant:

may send a Floor Release message towards other floor participants, if noqueued requests exist;

may enter the ‘O: silence’ state (1115).

In the FIG. 11, an operation for sending a floor granted message (PTTbutton released with pending request(s) in queue) (1124) is performed asfollows:

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send the Floor Granted message toward the other floor participants.The Floor Granted message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1123).

In the FIG. 11, an operation for receiving a floor request withpre-emption indication (R: Floor Request with pre-emption) (1124) isperformed as follows:

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send a Floor Granted message;

if floor control queuing mode is used in the session, the Floor Grantedmessage may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1123).

As to a state of ‘O: pending request’ (1103)

In this state the MCPTT client is waiting for a response to a Floorrequest message. The timer T11 (Request re-send) is running in thisstate.

In the FIG. 11, an operation for receiving RTP media (R: RTP media)(1101) is performed as follows:

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the RTP media packets; and,

may remain in ‘O: pending request’ state (1103).

In the FIG. 11, an operation for receiving Floor Request Queue Statusmessage (R: Floor Request Queue Status) is performed as follows;

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

may stop the timer T11 (Request re-send); and,

may enter ‘O: has no permission’ state.

In the FIG. 11, an operation for receiving a floor deny message (R:Floor Deny) (1104) is performed as follows:

Upon receiving Floor Deny message, the floor participant:

may stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

may enter ‘O: has no permission’ state (1110).

In the FIG. 11, an operation for sending a floor release message (PTTbutton released) (1106) is performed as follows:

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants;

may stop the timer T11 (request re-send); and,

may enter ‘O: silence’ state (1115).

In the FIG. 11, an operation for sending a floor taken message (TimerT11 fired N times and no media received) (1120) is performed as follows:

If no RTP media packet is received before the expiry of timer T11(request re-send) N times, the floor participant:

may send Floor Taken message towards other floor participants; and,

may enter ‘O: has permission’ state (1125).

In the FIG. 11, an operation for Timer T11 fired N times and Mediareceived is (1104) performed as follows:

If RTP media packet is received before the expiry of timer T11 (Requestre-send) N times, the floor participant: may enter ‘O: has nopermission’ state (1110).

In the FIG. 11, an operation for receiving a floor granted message (R:Floor Granted) (1120) is performed as follows:

Upon receiving Floor Granted message, the floor participant:

may stop timer T13 (No RTP Media), if the User ID in the Floor Grantedmessage matches its own User ID;

may stop the timer T11 (request re-send); and,

may enter ‘O: has permission state’ (1125)

In the FIG. 11, an operation for a T11 (Request re-send) timer fired(T11 timer fired) (1101) is performed as follows:

On firing of timer T11 (Request re-send), the floor participant:

may send the Floor Request message to other floor participants;

may restart the timer T11 (Request re-send); and,

may remain ‘O: pending request’ state (1103).

As to a state of ‘O: pending granted’ (1123)

In this state the MCPTT client is waiting for another client to takeover the role of floor controller. The Timer T20 (Granted re-send) isrunning in this state.

In the FIG. 11, an operation for receiving RTP Media (R: RTP Media) isperformed as follows:

Upon receiving the RTP media, the floor participant:

may stop timer T20 (Granted re-send);

may start timer T13 (no RTP media); and,

may enter ‘O: has no permission’ state (1110).

In the FIG. 11, an operation for a T20 (Granted re-send) timer fired(T20 timer fired) is performed as follows:

On firing of timer T20 (Granted re-send), the floor participant:

may send again the Floor Granted message toward the other floorparticipants. The Floor Granted message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue;

may restart the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state (1123).

In the FIG. 11, an operation for a T20 (Granted re-send) timer fired Ntimes with pending request(s) in the queue (T20 timer fired N times ANDpending request(s) in queue) (1119) is performed as follows:

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue, the floor participant:

may reset the count of N;

may send the Floor Granted message for the next pending request in thequeue towards

other floor participants. The Floor Granted message may be populated asfollows:

may indicate the User ID of the MCPTT client next in the floor requestqueue;

may indicate the SSRC of the MCPTT client next in the floor requestqueue;

may indicate the position of the MCPTT client next in the floor requestqueue;

may indicate the priority level of the MCPTT client next in the in thefloor request queue;

may start the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state (1123).

In the FIG. 11, an operation for a T20 (Granted re-send) timer fired Ntimes with no pending request in the queue (T20 timer fired N times ANDno pending request in queue) is performed as follows:

On the Nth firing of timer T20 (Granted re-send) and no pending requestin the queue, the floor participant:

may stop timer T20 (Granted re-send); and,

may enter ‘O: silence’ state (1115).

As to “Any state” (1107)

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’ stateand the ‘Releasing’ state.

In the FIG. 11, an operation for receiving MCPTT call release (R: MCPTTcall release) is performed as follows:

Upon receiving a MCPTT call release request from the application andsignaling plane when the MCPTT call is going to be released or when thefloor participant is leaving the MCPTT call, the floor participant:

may stop sending floor control messages towards other floorparticipants;

may request the MCPTT client to stop sending and receiving RTP mediapackets;

may release all resources including any running timers associated withthe MCPTT call;

may terminate the instance of floor participant state transitiondiagram; and,

may enter the ‘Start-stop’ state (1114).

In accordance with an aspect of the present disclosure, a detailedmethod of a floor participant state diagram with release state will bedescribed.

The floor participant may support the state diagram and the statetransitions specified in this subclause. When floor participant releasesthe permission sending media data, it may remain ‘O: release’ state.

FIG. 12 illustrates the floor participant state diagram with releasestate. State details are explained in the following subclauses.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant may discard thefloor control message or the RTP media packet and may remain in thecurrent state.

NOTE: A badly formatted RTP packet or floor control message received inany state is ignored by the floor participant and does not cause anychange of the current state.

Hereinafter, referring to the FIG. 12, operations in connection with thefloor participant state diagram with release state will be described indetail.

As to a state of “Start-stop” (12174)

In this state no state machine exists.

In the FIG. 12, an operation for MCPTT call established —originatingMCPTT user (1218) is performed as follows:

When a MCPTT call is established with session announcement including anexplicit floor request, the originating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine; and

may send Floor Taken message towards other floor participants; and

may enter the ‘O: has permission’ state (1226).

In the FIG. 12, an operation for MCPTT call established —terminatingMCPTT user (1212) is performed as follows:

When a MCPTT call is established the terminating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine; and

may enter the ‘O: silence’ state (1210).

As to a state of ‘O: silence’ (1210)

In this state a none of the MCPTT clients in the session is acting as afloor control server.

In the FIG. 12, an operation for sending a floor request message (PTTbutton pressed) (1205) is performed as follows:

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may send the Floor Request message to other floor participants; and

may enter ‘O: pending request’ state (1203).

In the FIG. 12, an operation for receiving RTP media (R: RTP media)(1201) is performed as follows:

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media);

may request the MCPTT client to start rendering received RTP mediapackets; and,

may enter ‘O: has no permission’ state (1211).

In the FIG. 12, an operation for receiving a floor taken message (R:Floor Taken) is performed as follows:

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media); and,

may enter ‘O: has no permission’ state (1211).

As to a state of ‘O: has no permission’ (1211)

In this state another floor participant does not have permission to sendmedia.

In the FIG. 12, an operation for sending a floor request message (PTTbutton pressed) (1205) is performed as follows:

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

may send the Floor Request message to other clients; and,

may enter ‘O: pending request’ state (1203).

In the FIG. 12, an operation for receiving a floor release message (R:Floor Release) is performed as follows:

When a Floor Release message is received, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter ‘O: silence’ state (1210); and,

may provide floor idle notification to the MCPTT user.

In the FIG. 12, an operation for a T13 (No RTP Media) timer fired (1213)is performed as follows:

On firing of T13 (No RTP Media) timer, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may enter ‘O: silence’ state (1210); and,

may provide floor idle notification to the MCPTT user.

In the FIG. 12, an operation for receiving a floor granted message (R:Floor Granted) (1204) is performed as follows:

When a Floor Granted message is received (i.e. when a Floor Request ispending in the queue or a higher priority request is pending), if theUser ID in the floor grant message matches its own User ID, the floorparticipant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter the state ‘O: has permission (1226); and,

may update the queue status and notify the MCPTT user.

Otherwise the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may restart timer T13 (No RTP Media);

may enter the state ‘O: has no permission’ (1211); and,

may update the queue status and notify the MCPTT user.

In the FIG. 12, an operation for receiving RTP media (R: RTP media)(1227) is performed as follows:

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may restart timer T13 (No RTP Media); and,

may remain in ‘O: has no permission’ state (1211).

In the FIG. 12, an operation for sending a floor release message (PTTbutton released) (1206) is performed as follows:

Upon receiving an indication from the MCPTT user to release the pendingrequest for the floor, the floor participant:

may send a Floor Release message towards other floor participants and,

may remain in ‘O: has no permission’ state (1211).

As to a state of ‘O: has permission’ (1226)

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

In the FIG. 12, an operation for sending RTP Media packets (S: RTPMedia) (1227) is performed as follows:

Upon receiving encoded media from the user or if encoded media isalready buffered the floor participant:

may request the MCPTT client to start sending RTP media packets towardsother MCPTT clients; and,

may remain in the ‘O: has permission’ state (1226).

In the FIG. 12, an operation for receiving a floor release message (R:Floor Release) (1204) is performed as follows:

Upon receiving a Floor Release message, the floor participant:

may remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and,

may remain in the ‘O: has permission’ state (1226).

In the FIG. 12, an operation for receiving a floor request (R: FloorRequest) (1204) is performed as follows:

When a Floor Request message is received in a session where queuing modeis not used, the floor participant:

may send the Floor Deny message including reason field toward the otherfloor participants; and,

may remain in the ‘O: has permission’ state (1226).

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher, thefloor participant:

may store the received Floor Request messages;

may send the Floor Request Queue Status message. The Floor Request QueueStatus message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may remain in the ‘O: has permission’ state (1226).

In the FIG. 12, an operation for sending a floor release message (PTTbutton released with no pending request in queue) is performed asfollows:

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant:

may send a Floor Release message towards other floor participants, if noqueued requests exist;

may enter the ‘O: release’ state (1230).

In the FIG. 12, an operation for sending a floor granted message (PTTbutton released with pending request(s) in queue) (1222) is performed asfollows:

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send the Floor Granted message toward the other floor participants.The Floor Granted message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1219).

Receive Floor Request with pre-emption indication (R: Floor Request withpre-emption) (1222) will be described below.

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

1. shall request the MCPTT client to stop sending RTP media packetstowards other MCPTT clients;

2. shall send a Floor Granted message;

3. if floor control queuing mode is used in the session, the FloorGranted message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

4. may enter the ‘O: pending granted’ state (1219).

State: ‘O: pending request’ (1203) will be described below.

In this state the MCPTT client is waiting for a response to a Floorrequest message.

The timer T11 (Request re-send) is running in this state.

Receive RTP media (R: RTP media) (1201) will be described below.

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the RTP media packets; and,

may remain in ‘O: pending request’ state (1203).

Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1204) will be described below.

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

may stop the timer T11 (Request re-send); and,

may enter ‘O: has no permission’ state (1211).

Receive Floor Deny message (R: Floor Deny) (1204) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

may stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

may enter ‘O: has no permission’ state (1211).

Send Floor Release message (PTT button released) (1207) will bedescribed below.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants;

may stop the timer T11 (request re-send); and,

may enter ‘O: silence’ state (1210).

Send Floor Taken message (Timer T11 fired N times and no media received)(1221) will be described below.

If no RTP media packet is received before the expiry of timer T11(request re-send) N times, the floor participant:

may send Floor Taken message towards other floor participants; and,

may enter ‘O: has permission’ state (1226)

Timer T11 fired N times and Media received (1204) will be describedbelow.

If RTP media packet is received before the expiry of timer T11 (Requestre-send) N times, the floor participant:

may enter ‘O: has no permission’ state (1211).

Receive Floor Granted message (R: Floor Granted) (1204) will bedescribed below.

Upon receiving Floor Granted message, if the User ID in the FloorGranted message matches its own User ID, the floor participant:

may stop timer T13 (No RTP Media);

may stop the timer T11 (request re-send); and,

may enter ‘O: has permission state’ (1226);

Otherwise the floor participant:

may stop the timer T11 (request re-send); and,

may enter ‘O: has no permission’ state (1211).

T11 (Request re-send) timer fired (T11 timer fired) (1201) will bedescribed below.

On firing of timer T11 (Request re-send), the floor participant:

may send the Floor Request message to other floor participants;

may restart the timer T11 (Request re-send); and,

may remain ‘O: pending request’ state (1203).

State: ‘O: pending granted’ (1219) will be described below.

In this state the MCPTT client is waiting for another client to takeover the role of floor controller.

The Timer T20 (Granted re-send) is running in this state.

Receive RTP Media (R: RTP Media) (1216) will be described below.

Upon receiving the RTP media, the floor participant:

may stop timer T20 (Granted re-send);

may start timer T13 (no RTP media); and,

may enter ‘O: has no permission’ state (1211).

T20 (Granted re-send) timer fired (T20 timer fired) (1220) will bedescribed below.

On firing of timer T20 (Granted re-send), the floor participant:

may send again the Floor Granted message toward the other floorparticipants. The Floor Granted message shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue;

may restart the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state (1219).

T20 (Granted re-send) timer fired N times with pending request(s) in thequeue (T20 timer fired N times AND pending request(s) in queue) (1220)will be described below.

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue, the floor participant:

may reset the count of N;

may send the Floor Granted message for the next pending request in thequeue towards other floor participants. The Floor Granted message shallbe populated as follows:

may indicate the User ID of the MCPTT client next in the floor requestqueue;

may indicate the SSRC of the MCPTT client next in the floor requestqueue;

may indicate the position of the MCPTT client next in the floor requestqueue;

may indicate the priority level of the MCPTT client next in the in thefloor request queue;

may start the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state (1219).

T20 (Granted re-send) timer fired N times with no pending request in thequeue (T20 timer fired N times AND no pending request in queue) (1215)will be described below.

On the N^(th) firing of timer T20 (Granted re-send) and no pendingrequest in the queue, the floor participant:

may stop timer T20 (Granted re-send); and,

may enter ‘O: silence’ state (1210).

State: ‘O: Release’ (1230) will be described below.

In this state a MCPTT client in the session is acting as a floor controlserver before other MCPTT client has the permission to send media.

Send Floor Request message (PTT button pressed) (1224) will be describedbelow.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may send the Floor Request message to other floor participants; and

may enter ‘O: pending request’ state (1203).

Receive RTP media (R: RTP media) (1227) will be described below.

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media);

may request the MCPTT client to start rendering received RTP mediapackets; and,

may enter ‘O: has no permission’ state (1211).

Receive Floor Taken message (R: Floor Taken) (1227) will be describedbelow.

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media); and,

may enter ‘O: has no permission’ state (1211).

Receive Floor Request (R: Floor Request) (1229) will be described below.

When a Floor Request message is received, the floor participant:

may send a Floor Granted message;

if floor control queuing mode is used in the session, the Floor Grantedmessage shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may should indicate the position of the MCPTT client in the floorrequest queue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1219).

State: Any state (1209) will be described below.

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’ stateand the ‘Releasing’ state.

Receive MCPTT call release (R: MCPTT call release) (1214) will bedescribed below.

Upon receiving a MCPTT call release request from the application andsignaling plane when the MCPTT call is going to be released or when thefloor participant is leaving the MCPTT call, the floor participant:

may stop sending floor control messages towards other floorparticipants;

may request the MCPTT client to stop sending and receiving RTP mediapackets;

may release all resources including any running timers associated withthe MCPTT call;

may terminate the instance of floor participant state transitiondiagram: and,

may enter the ‘Start-stop’ state (1217)

Next, Floor participant state diagram with release and queued state willbe described below.

The floor participant may support the state diagram and the statetransitions specified in this subclause.

Floor participant state diagram with release and queued state accordingto an embodiment of the present disclosure will be described withreference to FIG. 13

The floor participant state diagram —basic operation according to anembodiment of the present disclosure will be described with reference toFIG. 13.

FIG. 13 illustrates Floor participant state diagram with release andqueue state according to an embodiment of the present disclosure.

Referring to FIG. 13, State details are explained in the followingsubclauses.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant shall discard thefloor control message or the RTP media packet and shall remain in thecurrent state.

NOTE: A badly formatted RTP packet or floor control message received inany state is ignored by the floor participant and does not cause anychange of the current state.

State “Start-stop” (1321) will be described below

In this state no state machine exists.

MCPTT call established —originating MCPTT user (1323) will be describedbelow

When a MCPTT call is established with session announcement including anexplicit floor request, the originating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine; and

2. may send Floor Taken message towards other floor participants; and

3. may enter the ‘O: has permission’ state (1332).

MCPTT call established —terminating MCPTT user (1318) will be describedbelow.

When a MCPTT call is established the terminating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine; and

may enter the ‘O: silence’ state (1311).

Next, State: ‘O: silence’ (1311) will be described below.

In this state a none of the MCPTT clients in the session is acting as afloor control server.

Send Floor Request message (PTT button pressed) (1305) will be describedbelow.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may send the Floor Request message to other floor participants; and

may enter ‘O: pending request’ state (1303).

Receive RTP media (R: RTP media) (1306) will be described below

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media);

may request the MCPTT client to start rendering received RTP mediapackets; and,

may enter ‘O: has no permission’ state (1312).

Receive Floor Taken message (R: Floor Taken) (1306) will be describedbelow.

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media); and,

may enter ‘O: has no permission’ state (1312).

State: ‘O: has no permission’ (1312) will be described below.

In this state another floor participant does not have permission to sendmedia.

Sending Floor Request message (PTT button pressed) (1307) will bedescribed below.

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

may send the Floor Request message to other clients; and,

may enter ‘O: pending request’ state (1303).

Receive Floor Release message (R: Floor Release) (1315) will bedescribed below.

When a Floor Release message is received, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter ‘O: silence’ state (1311); and,

may provide floor idle notification to the MCPTT user.

T13 (No RTP Media) timer fired (1315) will be described below.

On firing of T13 (No RTP Media) timer, the floor participant:

1. may request the MCPTT client to stop rendering received RTP mediapackets;

may enter ‘O: silence’ state (1311); and,

may provide floor idle notification to the MCPTT user.

Receiving Floor Granted message (R: Floor Granted) (1307) will bedescribed below.

When a Floor Granted message is received (i.e. when a Floor Request ispending in the queue or a higher priority request is pending), if theUser ID in the floor grant message matches its own User ID, the floorparticipant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter the state ‘O: has permission (1332); and,

may update the queue status and notify the MCPTT user.

Otherwise the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may restart timer T13 (No RTP Media);

may enter the state ‘O: has no permission’ (1312); and

may update the queue status and notify the MCPTT user.

Receiving RTP media (R: RTP media) (1306) will be described below.

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may restart timer T13 (No RTP Media); and,

may remain in ‘O: has no permission’ state (1312).

Send Floor Release message (PTT button released) (1307) will bedescribed below.

Upon receiving an indication from the MCPTT user to release the pendingrequest for the floor, the floor participant:

may send a Floor Release message towards other floor participants; and,

may remain in ‘O: has no permission’ state (1312).

State: ‘O: has permission’ (1332) will be described below.

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

Send RTP Media packets (S: RTP Media) (1335) will be described below.

Upon receiving encoded media from the user or if encoded media isalready buffered the floor participant:

may request the MCPTT client to start sending RTP media packets towardsother MCPTT clients; and,

may remain in the ‘O: has permission’ state (1332).

Receive Floor Release message (R: Floor Release) (1335) will bedescribed below.

Upon receiving a Floor Release message, the floor participant:

may remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and,

may remain in the ‘O: has permission’ state (1332).

Receive Floor Request (R: Floor Request) (1335) will be described below.

When a Floor Request message is received in a session where queuing modeis not used, the floor participant:

may send the Floor Deny message including reason field toward the otherfloor participants; and,

may remain in the ‘O: has permission’ state (1332).

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher, thefloor participant:

may store the received Floor Request messages;

may send the Floor Request Queue Status message. The Floor Request QueueStatus message shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may remain in the ‘O: has permission’ state (1332).

Send Floor Release message (PTT button released with no pending requestin queue) (1334) will be described below.

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant:

may send a Floor Release message towards other floor participants, if noqueued requests exist;

may enter the ‘O: release’ state (1336).

Send Floor Granted message (PTT button released with pending request(s)in queue) (1329) will be described below.

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send the Floor Granted message toward the other floor participants.The Floor Granted message shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1324).

Receive Floor Request with pre-emption indication (R: Floor Request withpre-emption) (1329) will be described below.

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send a Floor Granted message;

if floor control queuing mode is used in the session, the Floor Grantedmessage shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may enter the ‘O: pending granted’ state (1324).

State: ‘O: pending request’ (1303) will be described below.

In this state the MCPTT client is waiting for a response to a Floorrequest message.

The timer T11 (Request re-send) is running in this state.

Receive RTP media (R: RTP media) (1301) will be described below.

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the RTP media packets; and,

may remain in ‘O: pending request’ state (1303).

Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1309) will be described below.

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

may stop the timer T11 (Request re-send); and,

may enter ‘O: queued’ state (1313).

Receive Floor Deny message (R: Floor Deny) (1304) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

may stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

may enter ‘O: has no permission’ state (1312).

Send Floor Release message (PTT button released) (1302) will bedescribed below.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants;

may stop the timer T11 (request re-send); and,

may enter ‘O: silence’ state (1311).

Send Floor Taken message (Timer T11 fired N times and no media received)(1328)

If no RTP media packet is received before the expiry of timer T11(request re-send) N times, the floor participant:

may send Floor Taken message towards other floor participants; and,

may enter ‘O: has permission’ state (1332).

Timer T11 fired N times and Media received (1304) will be describedbelow.

If RTP media packet is received before the expiry of timer T11 (Requestre-send) N times, the floor participant:

may enter ‘O: has no permission’ state (1312).

Receive Floor Granted message (R: Floor Granted) (1328) will bedescribed below.

Upon receiving Floor Granted message, if the User ID in the FloorGranted message matches its own User ID, the floor participant:

may stop timer T13 (No RTP Media);

may stop the timer T11 (request re-send); and

may enter ‘O: has permission state’ (1332);

Otherwise the floor participant:

may stop the timer T11 (request re-send); and

may enter ‘O: has no permission’ state (1312)

T11 (Request re-send) timer fired (T11 timer fired) (1301) will bedescribed below.

On firing of timer T11 (Request re-send), the floor participant:

may send the Floor Request message to other floor participants;

may restart the timer T11 (Request re-send); and,

may remain ‘O: pending request’ state (1303).

State: ‘O: pending granted’ (1324) will be described below.

In this state the MCPTT client is waiting for another client to takeover the role of floor controller.

The Timer T20 (Granted re-send) is running in this state.

Receive RTP Media (R: RTP Media) (1319) will be described below.

Upon receiving the RTP media, the floor participant:

may stop timer T20 (Granted re-send);

may start timer T13 (no RTP media); and,

may enter ‘O: has no permission’ state (1312)

T20 (Granted re-send) timer fired (T20 timer fired) (1325) will bedescribed below.

On firing of timer T20 (Granted re-send), the floor participant:

may send again the Floor Granted message toward the other floorparticipants. The Floor Granted message shall be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue;

may restart the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state (1324).

T20 (Granted re-send) timer fired N times with pending request(s) in thequeue (T20 timer fired N times AND pending request(s) in queue) (1325)will be described below.

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue, the floor participant:

may reset the count of N;

may send the Floor Granted message for the next pending request in thequeue towards other floor participants. The Floor Granted message shallbe populated as follows:

may indicate the User ID of the MCPTT client next in the floor requestqueue;

may indicate the SSRC of the MCPTT client next in the floor requestqueue;

may indicate the position of the MCPTT client next in the floor requestqueue;

may indicate the priority level of the MCPTT client next in the in thefloor request queue;

may start the timer T20 (Granted re-send); and,

may remain ‘O: pending granted’ state.

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue (T20 timer fired N times AND pending request(s) inqueue) 1325, the floor participant may reset the count of N, and maysend the Floor Granted message for the next pending request in the queuetowards other floor participants. The Floor Granted message may bepopulated as follows. The Floor Granted message should indicate the UserID of the MCPTT client next in the floor request queue. The FloorGranted message should indicate the SSRC of the MCPTT client next in thefloor request queue. The Floor Granted message should indicate theposition of the MCPTT client next in the floor request queue. The FloorGranted message should indicate the priority level of the MCPTT clientnext in the in the floor request queue. Then, the floor participant maystart the timer T20 (Granted re-send). Then, the floor participant mayremain ‘O: pending granted’ state 1324.

On the N^(th) firing of timer T20 (Granted re-send) and no pendingrequest in the queue (T20 timer fired N times AND no pending request inqueue) 1322, the floor participant may stop timer T20 (Granted re-send).Then, the floor participant may enter ‘O: silence’ state 1311.

A state ‘O: Release’ 1336 will be described below.

In this state, a MCPTT client in the session is acting as a floorcontrol server before other MCPTT client has the permission to sendmedia.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant may send the Floor Request message(PTT button pressed) 1330 to other floor participants, and may enter ‘O:pending request’ state 1303.

Upon receiving RTP media packets (R: RTP media) 1333, the floorparticipant may provide a floor taken notification to the MCPTT user,may start timer T13 (No RTP Media), may request the MCPTT client tostart rendering received RTP media packets, and then, may enter ‘O: hasno permission’ state 1312.

Upon receiving Floor Taken message (R: Floor Taken) 1333, the floorparticipant may provide a floor taken notification to the MCPTT user,may start timer T13 (No RTP Media), and then, may enter ‘O: has nopermission’ state 1312.

When a Floor Request message is received (R: Floor Request) 1331, thefloor participant may send a Floor Granted message. If floor controlqueuing mode is used in the session, the Floor Granted message may bepopulated as follows. The Floor Granted message should indicate the UserID of the MCPTT client in the floor request queue. The Floor Grantedmessage should indicate the SSRC of the MCPTT client in the floorrequest queue. The Floor Granted message should indicate the position ofthe MCPTT client in the floor request queue. The Floor Granted messageshould indicate the priority level of the MCPTT client in the in thefloor request queue. Then, the floor participant may enter the ‘O:pending granted’ state 1324.

A State ‘O: queued’ 1313 will be described below.

In this state the MCPTT client is waiting for a response to a pendingrequest.

Upon receiving RTP media packets (R: RTP media) 1314, the floorparticipant may request the MCPTT client to render the RTP mediapackets, and may then, remain in ‘O: queued’ state 1313.

Upon receiving Floor Request Queue Status message (R: Floor RequestQueue Status) 1314, the floor participant may update the queue status,if the User ID in the Floor Request Queue Status message matches its ownUser ID, may notify the MCPTT user about the queue position, and then,may remain in ‘O: queued’ state 1313.

Upon receiving Floor Deny message (R: Floor Deny) 1316, the floorparticipant may enter ‘O: has no permission’ state 1312.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant may send a FloorRelease message (PTT button released) 1316 towards other floorparticipants, and then, may enter ‘O: has no permission’ state 1312.

Upon receiving Floor Granted message (R: Floor Granted) 1316, if theUser ID in the Floor Granted message matches its own User ID, the floorparticipant may stop timer T13 (No RTP Media), and, may enter ‘O: haspermission state’ 1332. Otherwise the floor participant may enter ‘O:has no permission’ state 1312.

On firing of T13 (No RTP Media) timer 1310, the floor participant mayrequest the MCPTT client to stop rendering received RTP media packets,may enter ‘O: silence’ state 1311, and then, may provide floor idlenotification to the MCPTT user.

A state ‘Any state’ 1317 will be described below.

The actions to be taken in all states defined for the basic statediagram with the exception of the ‘Start-stop’ state and the ‘Releasing’state will be described below.

Upon receiving a MCPTT call release request (R: MCPTT call release) 1320from the application and signaling plane when the MCPTT call is going tobe released or when the floor participant is leaving the MCPTT call, thefloor participant may stop sending floor control messages towards otherfloor participants, may request the MCPTT client to stop sending andreceiving RTP media packets, may release all resources including anyrunning timers associated with the MCPTT call, may terminate theinstance of floor participant state transition diagram, and then, mayenter the ‘Start-stop’ state 1321.

FIG. 14 is a floor participant state diagram with queuing operation ofautomatic way. Referring to FIG. 14, The floor participant may supportthe state diagram and the state transitions specified below.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant may discard thefloor control message or the RTP media packet and may remain in thecurrent state. A badly formatted RTP packet or floor control messagereceived in any state is ignored by the floor participant and does notcause any change of the current state.

A State “Start-stop” 1416 will be described below.

In this state no state machine exists.

When a MCPTT call originating MCPTT user is established with sessionannouncement including an explicit floor request 1425, the originatingfloor participant may create an instance of a floor participant statetransition diagram for basic operation state machine, may send FloorTaken message towards other floor participants, may start timer T30(During silence), and may enter the ‘O: has permission’ state 1430.

When a MCPTT call terminating MCPTT user is established 1414, theterminating floor participant may create an instance of a floorparticipant state transition diagram for basic operation state machine,may start timer T30 (During silence), and may enter the ‘O: silence’state 1412.

A State: ‘O: silence’ 1412 will be described below.

In this state a none of the MCPTT clients in the session is acting as afloor control server.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant may send the Floor Request message(PTT button pressed) to other floor participants 1405, may start thetimer T11 (Request re-send), and may enter ‘O: pending request’ state1402.

Upon receiving RTP media packets (R: RTP media) 1408, the floorparticipant may provide a floor taken notification to the MCPTT user,may restart timer T30 (During silence), may restart (or start, if notrunning already) timer T13 (No RTP Media), may request the MCPTT clientto start rendering received RTP media packets; and then may enter ‘O:has no permission’ state 1410.

Upon receiving Floor Taken message (R: Floor Taken) 1408, the floorparticipant may provide a floor taken notification to the MCPTT user,may start timer T13 (No RTP Media), and then may enter ‘O: has nopermission’ state 1410.

A State ‘O: has no permission’ 1409 will be described below.

In this state another floor participant does not have permission to sendmedia.

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant may send the FloorRequest message to other clients (PTT button pressed) 1401, may startthe timer T11 (Request re-send), and may enter ‘O: pending request’state 1403.

When a Floor Release message is received (R: Floor Release) 1413, thefloor participant may request the MCPTT client to stop renderingreceived RTP media packets, may stop timer T13 (No RTP Media), may enter‘O: silence’ state 1412, and may provide floor idle notification to theMCPTT user.

On firing of T13 (No RTP Media) timer 1413, the floor participant mayrequest the MCPTT client to stop rendering received RTP media packetsmay enter ‘O: silence’ state 1412, and then, may provide floor idlenotification to the MCPTT user.

When a Floor Granted message is received (R: Floor Granted to other)1409 and if the User ID in the Floor Granted message dose not match itsown User ID, the floor participant may request the MCPTT client to stoprendering received RTP media packets, and may remain in ‘O: has nopermission’ state 1410.

Upon receiving RTP media packets (R: RTP media) 1409, the floorparticipant may request the MCPTT client to render the received RTPmedia packets, may restart timer T30 (During silence), may restart timerT13 (No RTP Media), and then, may remain in ‘O: has no permission’ state1410.

A State ‘O: has permission’ 1430 will be described below.

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

Upon receiving encoded media from the user or if encoded media isalready buffered, the floor participant may request the MCPTT client tostart sending RTP media packets towards other MCPTT clients (S: RTPMedia) 1431, may restart timer T30 (During silence), and then, mayremain in the ‘O: has permission’ state 1430.

Upon receiving a Floor Release message (R: Floor Release) 1431, thefloor participant may remove the sender of the Floor Release messagefrom the queue, if the User ID in the floor release message matches thequeued request of User ID, and then, may remain in the ‘O: haspermission’ state 1430.

When a Floor Request message is received (R: Floor Request) 1431 in asession where queuing mode is not used, the floor participant may sendthe Floor Deny message including reason field toward the other floorparticipants, and then, may remain in the ‘O: has permission’ state1430.

When a Floor Request message is received (R: Floor Request) 1431 in asession where queuing mode is used and if the priority level of themessage is not higher, the floor participant may store the receivedFloor Request messages, may send the Floor Request Queue Status message.The Floor Request Queue Status message may be populated as follows. TheFloor Request Queue Status message should indicate the User ID of theMCPTT client in the floor request queue. The Floor Request Queue Statusmessage should indicate the SSRC of the MCPTT client in the floorrequest queue. The Floor Request Queue Status message should indicatethe position of the MCPTT client in the floor request queue. The FloorRequest Queue Status message should indicate the priority level of theMCPTT client in the in the floor request queue. Then, floor participantmay remain in the ‘O: has permission’ state 1431.

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant may send a Floor Releasemessage towards other floor participants, if no queued requests exist(PTT button released with no pending request in queue) 1421, and then,may enter the ‘O: silence’ state 1412.

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant may request the MCPTT client to stopsending RTP media packets towards other MCPTT clients, and may send theFloor Granted message toward the other floor participants (PTT buttonreleased with pending request(s) in queue) 1429. The Floor Grantedmessage may be populated as follows. The Floor Granted message shouldindicate the list of User IDs of the MCPTT clients in the floor requestqueue. The Floor Granted message should indicate the list of SSRCs ofthe MCPTT clients in the floor request queue. The Floor Granted messageshould indicate the list of positions of the MCPTT clients in the floorrequest queue. The Floor Granted message should indicate the list ofpriority levels of the MCPTT clients in the in the floor request queue.Then, the floor participant may start timer T20 (Granted re-send), andthen, may enter the ‘O: pending granted’ state 1422.

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant (R: Floor Request withpre-emption) 1429, the floor participant may request the MCPTT client tostop sending RTP media packets towards other MCPTT clients, may send aFloor Granted message may start timer T20 (Granted re-send), and iffloor control queuing mode is used in the session, the Floor Grantedmessage may be populated as follows. The Floor Granted message shouldindicate the list of User IDs of the MCPTT clients in the floor requestqueue. The Floor Granted message should indicate the list of SSRCs ofthe MCPTT clients in the floor request queue. The Floor Granted messageshould indicate the list of positions of the MCPTT clients in the floorrequest queue. The Floor Granted message should indicate the list ofpriority levels of the MCPTT clients in the in the floor request queue.Then, the floor participant may enter the ‘O: pending granted’ state1422.

A State ‘O: pending request’ 1403 will be described below.

In this state the MCPTT client is waiting for a response to a Floorrequest message.

Upon receiving RTP media packets (R: RTP media) 1402, the floorparticipant may request the MCPTT client to render the RTP mediapackets, may restart timer T30 (During silence), may restart (or start,if not running already) the timer T13 (No RTP media), and then, mayremain in ‘O: pending request’ state 1403.

Upon receiving Floor Request Queue Status message (R: Floor RequestQueue Status) 1415, the floor participant may update the queue status,if the User ID in the Floor Request Queue Status message matches its ownUser ID, may notify the MCPTT user about the queue position, may stopthe timer T11 (Request re-send); and then, may enter ‘O: queued’ state1424.

Upon receiving Floor Deny message (R: Floor Deny) 1404, the floorparticipant may stop the timer T11 (Request re-send), if the User ID inthe Floor Deny message matches its own User ID, and then, may enter ‘O:has no permission’ state 1410.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant may send a FloorRelease message (PTT button released) 1405 towards other floorparticipants may stop the timer T11 (request re-send), and then, mayenter ‘O: silence’ state 1412.

If no RTP media packet is received before the expiry of timer T11(request re-send) N times (Timer T11 fired N times and no mediareceived) 1420, the floor participant may send Floor Taken messagetowards other floor participants, may stop timer T13 (no RTP media), ifrunning, and then, may enter ‘O: has permission’ state 1430.

If RTP media packet is received before the expiry of timer T11 (Requestre-send) N times 1404, the floor participant may enter ‘O: has nopermission’ state 1410.

Upon receiving Floor Granted message (R: Floor Granted to me) 1420, ifthe User ID in the Floor Granted message matches its own User ID, thefloor participant may stop timer T13 (No RTP Media), if running, maystop the timer T11 (request re-send), and then, may enter ‘O: haspermission state’ 1430.

Upon receiving Floor Granted message (R: Floor Granted to other) 1402and if the User ID in the Floor Granted message does not match its ownUser ID, the floor participant may request the MCPTT client to stoprendering received RTP media packets, and then, may remain in ‘O:pending request’ state 1403.

On firing of timer T11 (Request re-send) (T11 timer fired) 1402, thefloor participant may send the Floor Request message to other floorparticipants, may restart the timer T11 (Request re-send), and then mayremain ‘O: pending request’ state 1403.

A State ‘O: pending granted’ 1422 will be described below.

In this state the MCPTT client is waiting for another client to takeover the role of floor controller. The Timer T20 (Granted re-send) isrunning in this state.

Upon receiving the RTP media (R: RTP Media) 1419, the floor participantmay request the MCPTT client to render the received RTP media packets,may stop timer T20 (Granted re-send), may restart timer T30 (Duringsilence), may start timer T13 (no RTP media), and then, may enter ‘O:has no permission’ state 1410.

On firing of timer T20 (Granted re-send) (T20 timer fired) 1436, thefloor participant may send again the Floor Granted message toward theother floor participants. The Floor Granted message may be populated asfollows. The Floor Granted message should indicate the list of User IDsof the MCPTT clients in the floor request queue. The Floor Grantedmessage should indicate the list of SSRCs of the MCPTT clients in thefloor request queue. The Floor Granted message. The Floor Grantedmessage should indicate the list of positions of the MCPTT clients inthe floor request queue. The Floor Granted message should indicate thelist of priority levels of the MCPTT clients in the in the floor requestqueue. Then, the floor participant may restart the timer T20 (Grantedre-send), and, may remain ‘O: pending granted’ state 1422.

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue (T20 timer fired N times AND pending request(s) inqueue) 1436, the floor participant may reset the count of N, and maysend the Floor Granted message for the next pending request in the queuetowards other floor participants. The Floor Granted message may bepopulated as follows. The Floor Granted message should indicate the listof User IDs of the MCPTT clients next in the floor request queue. TheFloor Granted message should indicate the list of SSRCs of the MCPTTclients next in the floor request queue. The Floor Granted messageshould indicate the list of positions of the MCPTT clients next in thefloor request queue. The Floor Granted message should indicate the listof priority levels of the MCPTT clients next in the in the floor requestqueue. Then, the floor participant may start the timer T20 (Grantedre-send), and, may remain ‘O: pending granted’ state 1422.

On the N^(th) firing of timer T20 (Granted re-send) and no pendingrequest in the queue (T20 timer fired N times AND no pending request inqueue) 1418, the floor participant may stop timer T20 (Granted re-send),and then, may enter ‘O: silence’ state 1412.

A State: ‘O: queued’ 1424 will be described below.

In this state the MCPTT client is waiting for a response to a pendingrequest.

Upon receiving RTP media packets (R: RTP media) 1427, the floorparticipant may request the MCPTT client to render the RTP mediapackets, may restart timer T30 (During silence), may restart timer T13(no RTP media), and then, may remain in ‘O: queued’ state 1424.

Upon receiving Floor Request Queue Status message (R: Floor RequestQueue Status) 1427, the floor participant may update the queue status,if the User ID in the Floor Request Queue Status message matches its ownUser ID, may notify the MCPTT user about the queue position, and then,may remain in ‘O: queued’ state.

Upon receiving Floor Deny message (R: Floor Deny) 1423, the floorparticipant may enter ‘O: has no permission’ state 1410.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant may send a FloorRelease message towards other floor participants (PTT button released)1423, and then, may enter ‘O: has no permission’ state 1410.

Upon receiving Floor Granted message (R: Floor Granted to me) 1428, ifthe User ID in the Floor Granted message matches its own User ID, thefloor participant may request the MCPTT client to stop renderingreceived RTP media packets, may stop timer T13 (No RTP Media), and, mayenter ‘O: has permission’ state 1430.

Upon receiving Floor Granted message (R: Floor Granted to other) 1427and if the User ID in the Floor Granted message does not match its ownUser ID, the floor participant may request the MCPTT client to stoprendering received RTP media packets, and then, may remain in ‘O:queued’ state 1427.

On firing of T13 (No RTP Media) timer 1417, the floor participant mayrequest the MCPTT client to stop rendering received RTP media packets,may enter ‘O: silence’ state 1412, and then, may provide floor idlenotification to the MCPTT user.

On firing of T13 (No RTP Media) timer 1417, the floor participant mayrequest the MCPTT client to stop rendering received RTP media packets,may enter ‘O: silence’ state, and then, may provide floor idlenotification to the MCPTT user.

As to State: Any state is disclosed.

FIG. 15 show the floor participant state diagram.

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’ state(1518).

Receive MCPTT call release (R: MCPTT call release) (1511) Upon receivinga MCPTT call release request from the application and signaling planewhen the MCPTT call is going to be released or when the floorparticipant is leaving the MCPTT call, the floor participant: may stopsending floor control messages towards other floor participants; mayrequest the MCPTT client to stop sending and receiving RTP mediapackets; may release all resources including any running timersassociated with the MCPTT call; may terminate the instance of floorparticipant state transition diagram; and, may enter the ‘Start-stop’state (1518).

As to Floor participant state diagram with queuing operation of manualway

The floor participant may support the state diagram and the statetransitions specified in this subclause.

State details are explained in the following subclauses.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant may discard thefloor control message or the RTP media packet and may remain in thecurrent state.

A badly formatted RTP packet or floor control message received in anystate is ignored by the floor participant and does not cause any changeof the current state.

As to State “Start-stop” (1518)

In this state no state machine exists.

As to MCPTT call established —originating MCPTT user (1525)

When a MCPTT call is established with session announcement including anexplicit floor request, the originating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine;

may send Floor Taken message towards other floor participants;

may start timer T30 (During silence); and,

may enter ‘O: has permission’ state (1531).

As to MCPTT call established —terminating MCPTT user (1514)

When a MCPTT call is established the terminating floor participant:

may create an instance of a floor participant state transition diagramfor basic operation state machine;

may start timer T30 (During silence); and,

may enter ‘O: silence’ state (1512).

As to State: ‘O: silence’ (1512)

In this state a none of the MCPTT clients in the session is acting as afloor control server.

As to Send Floor Request message (PTT button pressed) (1508)

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may send the Floor Request message to other floor participants;

may start the timer T11 (Request re-send); and,

may enter ‘O: pending request’ state (1503).

As to Receive RTP media (R: RTP media) (1501)

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

may restart timer T30 (During silence);

may restart (or start, if not running already) timer T13 (No RTP Media);

may request the MCPTT client to start rendering received RTP mediapackets; and,

may enter ‘O: has no permission’ state (1510).

As to Receive Floor Taken message (R: Floor Taken) (1509)

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

may start timer T13 (No RTP Media); and,

may enter ‘O: has no permission’ state (1510).

As to State: ‘O: has no permission’ (1510)

In this state another floor participant does not have permission to sendmedia.

As to Sending Floor Request message (PTT button pressed)(1502)

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

may send the Floor Request message to other clients;

may start the timer T11 (Request re-send); and,

may enter ‘O: pending request’ state (1503).

As to Receive Floor Release message (R: Floor Release) (1513)

When a Floor Release message is received, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media);

may enter ‘O: silence’ state; and,

may provide floor idle notification to the MCPTT user.

As to T13 (No RTP Media) timer fired (1513)

On firing of T13 (No RTP Media) timer, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may enter ‘O: silence’ state (1512); and,

may provide floor idle notification to the MCPTT user.

As to Receiving Floor Granted message (R: Floor Granted to other) (1506)

When a Floor Granted message is received and if the User ID in the FloorGranted message dosen't match its own User ID, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets; and,

may remain in ‘O: has permission’ state.

As to Receiving RTP media (R: RTP media) (1506)

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may restart timer T30 (During silence);

may restart timer T13 (No RTP Media); and,

may remain in ‘O: has no permission’ state (1510).

As to State: ‘O: has permission’ (1531)

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

As to Send RTP Media packets (S: RTP Media) (1532)

Upon receiving encoded media from the user or if encoded media isalready buffered the floor participant:

may request the MCPTT client to start sending RTP media packets towardsother MCPTT clients;

may restart timer T30 (During silence); and,

may remain in ‘O: has permission’ state (1531).

As to Receive Floor Release message (R: Floor Release) (1532)

Upon receiving a Floor Release message, the floor participant:

may remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and,

may remain in ‘O: has permission’ state (1531).

As to Receive Floor Request (R: Floor Request) (1532)

When a Floor Request message is received in a session where queuing modeis not used, the floor participant:

may send the Floor Deny message including reason field toward the otherfloor participants; and,

may remain in ‘O: has permission’ state (1531).

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher, thefloor participant:

may store the received Floor Request messages;

may send the Floor Request Queue Status message. The Floor Request QueueStatus message may be populated as follows:

may indicate the User ID of the MCPTT client in the floor request queue;

may indicate the SSRC of the MCPTT client in the floor request queue;

may indicate the position of the MCPTT client in the floor requestqueue;

may indicate the priority level of the MCPTT client in the in the floorrequest queue; and,

may remain in ‘O: has permission’ state (1531).

As to Send Floor Release message (PTT button released with no pendingrequest in queue) (1521)

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant:

may send a Floor Release message towards other floor participants, if noqueued requests exist; and,

may enter ‘O: silence’ state (1512).

As to Send Floor Granted message (PTT button released with pendingrequest(s) in queue) (1530)

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send the Floor Granted message toward the other floor participants.

The Floor Granted message may be populated as follows:

may indicate the list of User IDs of the MCPTT clients in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients in the floor requestqueue;

may indicate the list of positions of the MCPTT clients in the floorrequest queue;

may indicate the list of priority levels of the MCPTT clients in the inthe floor request queue;

may start timer T20 (Granted re-send); and,

may enter ‘O: pending granted’ state (1522).

As to Receive Floor Request with pre-emption indication (R: FloorRequest with pre-emption) (1530)

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send a Floor Granted message;

may start timer T20 (Granted re-send);

if floor control queuing mode is used in the session, the Floor Grantedmessage may be populated as follows:

may indicate the list of User IDs of the MCPTT clients in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients in the floor requestqueue;

may indicate the list of positions of the MCPTT clients in the floorrequest queue;

may indicate the list of priority levels of the MCPTT clients in the inthe floor request queue; and,

may enter ‘O: pending granted’ state (1522).

As to State: ‘O: pending request’ (1503)

In this state the MCPTT client is waiting for a response to a Floorrequest message.

As to Receive RTP media (R: RTP media) (1501)

Upon receiving RTP media packets, the floor participant:

may request the MCPTT client to render the RTP media packets;

may restart timer T30 (During silence);

may restart (or start, if not running already) the timer T13 (No RTPmedia); and,

may remain in ‘O: pending request’ state (1503).

As to Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1517)

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

may stop the timer T11 (Request re-send); and,

may enter ‘O: queued’ state (1524).

As to Receive Floor Deny message (R: Floor Deny) (1504)

Upon receiving Floor Deny message, the floor participant:

may stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

may enter ‘O: has no permission’ state (1510).

As to Send Floor Release message (PTT button released) (1508)

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants;

may stop the timer T11 (request re-send); and,

may enter ‘O: silence’ state (1512).

As to Send Floor Taken message (Timer T11 fired N times and no mediareceived) (1520)

If no RTP media packet is received before the expiry of timer T11(request re-send) N times, the floor participant:

may send Floor Taken message towards other floor participants;

may stop timer T13 (no RTP media), if running; and,

may enter ‘O: has permission’ state (1531).

As to Receive Floor Granted message (R: Floor Granted to me) (1520)

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media), if running;

may stop the timer T11 (request re-send); and,

may enter ‘O: has permission’ state (1531).

As to Receive Floor Granted message (R: Floor Granted to other) (1501)

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets; and,

may remain in ‘O: pending request’ state (1503).

As to T11 (Request re-send) timer fired (T11 timer fired) (1501)

On firing of timer T11 (Request re-send), the floor participant:

may send the Floor Request message to other floor participants;

may restart the timer T11 (Request re-send); and,

may remain in ‘O: pending request’ state (1503).

As to Timer T11 fired N times and Media received (1504)

If RTP media packet is received before the expiry of timer T11 (Requestre-send) N times, the floor participant:

may enter ‘O: has no permission’ state (1510).

As to State: ‘O: pending granted’ (1522)

In this state the MCPTT client is waiting for another client to takeover the role of floor controller.

The Timer T20 (Granted re-send) is running in this state.

As to Receive RTP Media (R: RTP Media) (1516)

Upon receiving the RTP media, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may stop timer T20 (Granted re-send);

may restart timer T30 (During silence);

may start timer T13 (no RTP media); and,

may enter ‘O: has no permission’ state (1510).

As to T20 (Granted re-send) timer fired (T20 timer fired) (1527)

On firing of timer T20 (Granted re-send), the floor participant:

may send again the Floor Granted message toward the other floorparticipants. The Floor Granted message may be populated as follows:

may indicate the list of User IDs of the MCPTT clients in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients in the floor requestqueue;

may indicate the list of positions of the MCPTT clients in the floorrequest queue;

may indicate the list of priority levels of the MCPTT clients in the inthe floor request queue;

may restart the timer T20 (Granted re-send); and,

may remain in ‘O: pending granted’ state (1522).

As to T20 (Granted re-send) timer fired N times (1527)

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue, the floor participant:

may reset the count of N;

may start the timer T33 (Pending user action); and,

may remain in ‘O: pending granted’ state (1522).

As to T33 (Pending user action) timer fired with no pending request inthe queue (T33 timer fired AND no pending request in queue) (1515)

On the firing of timer T33 (Pending user action) with no pending requestin the queue, the floor participant:

may send a Floor Release message towards other floor participants; and,

may enter ‘O: silence’ state (1512).

As to T33 (Pending user action) timer fired with pending request(s) inthe queue (T33 timer fired AND pending request(s) in queue)

On the firing of timer T33 (Pending user action) with more request(s)pending in the queue, the floor participant:

may send the Floor Granted message for the next pending request in thequeue towards other floor participants. The Floor Granted message may bepopulated as follows:

may indicate the list of User IDs of the MCPTT clients next in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients next in the floorrequest queue;

may indicate the list of positions of the MCPTT clients next in thefloor request queue;

may indicate the list of priority levels of the MCPTT clients next inthe in the floor request queue;

may start the timer T20 (Granted re-send); and,

may remain in ‘O: pending granted’ state (1522).

As to State: ‘O: queued (1524)

In this state the MCPTT client is waiting for a response to a pendingrequest.

As to Receive RTP media (R: RTP media) (1528)

Upon receiving RTP media packets, the floor participant:

16. may request the MCPTT client to render the RTP media packets;

17. may restart timer T30 (During silence);

18. may restart timer T13 (no RTP media); and,

19. may remain in ‘O: queued’ state (1524).

As to Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1528)

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position; and,

may remain in ‘O: queued’ state (1524).

As to Receive Floor Deny message (R: Floor Deny) (1523)

Upon receiving Floor Deny message, the floor participant:

may enter ‘O: has no permission’ state (1510).

As to Send Floor Release message (S: Floor Release) (1523)

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants; and,

may enter ‘O: has no permission’ state (1510).

As to Receiving Floor Granted message (R: Floor Granted to me) (1528)

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may start timer T33 (Pending user action); and,

may remain in ‘O: queued’ state (1524).

As to T33 (Pending user action) timer fired (1523)

1. may start timer T30 (During silence); and, may enter ‘O: has nopermission’ state (1510).

As to PTT button pressed (1529)

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

may stop the timer T33 (Pending user action); and,

may enter ‘O: has permission’ state (1531).

As to Receive Floor Granted message (R: Floor Granted to other) (1528)

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets; and,

may stop timer T30 (During silence); and;

may remain in ‘O: queued’ state (1524).

As to T13 (No RTP Media) timer fired (1519)

On firing of T13 (No RTP Media) timer, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may enter ‘O: silence’ state (1512); and,

may provide floor idle notification to the MCPTT user.

As to State: Any state (1507)

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’state.

As to Receive MCPTT call release (R: MCPTT call release) (1511)

Upon receiving a MCPTT call release request from the application andsignaling plane when the MCPTT call is going to be released or firing oftimer T30 (During silence), the floor participant:

may stop sending floor control messages towards other floorparticipants;

may request the MCPTT client to stop sending and receiving RTP mediapackets;

may release all resources including any running timers associated withthe MCPTT call;

may terminate the instance of floor participant state transitiondiagram; and,

may enter ‘Start-stop’ state (1518).

As to Floor participant state diagram with resolving race condition ofmultiple floor request

The floor participant may support the state diagram and the statetransitions specified in this subclause.

FIG. 16 show the ‘Floor participant state diagram —basic operation’.

State details are explained in the following subclauses.

If an RTP media packet or a floor control message arrives in a statewhere there is no specific procedure specified for the RTP media or thereceived floor control message, the floor participant shall discard thefloor control message or the RTP media packet and shall remain in thecurrent state.

NOTE: A badly formatted RTP packet or floor control message received inany state is ignored by the floor participant and does not cause anychange of the current state.

State “Start-stop” (1621) will be described below.

In this state no state machine exists.

MCPTT call established —originating MCPTT user (1631) will be describedbelow.

When an MCPTT call is established with session announcement including anexplicit floor request, the originating floor participant: shall createan instance of a floor participant state transition diagram for basicoperation state machine;

shall send Floor Taken message towards other floor participants;

shall start timer T30 (During silence); and

shall enter ‘O: has permission’ state (1635).

MCPTT call established —terminating MCPTT user (1618) will be describedbelow.

When an MCPTT call is established the terminating floor participant:

shall create an instance of a floor participant state transition diagramfor basic operation state machine;

shall start timer T30 (During silence); and

shall enter ‘O: silence’ state (1615).

State: ‘O: silence’ (1615) will be described below.

In this state a none of the MCPTT clients in the session is acting as afloor control server.

Send Floor Request message (PTT button pressed) (1605) will be describedbelow.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

shall send the Floor Request message to other floor participants;

shall start the timer T11 (Request re-send); and

shall enter ‘O: pending request’ state (1604).

Receive RTP media (R: RTP media) (1610) will be described below.

Upon receiving RTP media packets, the floor participant:

may provide a floor taken notification to the MCPTT user;

shall restart timer T30 (During silence);

shall restart (or start, if not running already) timer T13 (No RTPMedia);

shall request the MCPTT client to start rendering received RTP mediapackets; and

shall enter ‘O: has no permission’ state (1611).

Receive Floor Taken message (R: Floor Taken) (1610) will be describedbelow.

Upon receiving Floor Taken message, the floor participant:

may provide a floor taken notification to the MCPTT user;

shall start timer T13 (No RTP Media); and

Shall enter ‘O: has no permission’ state (1611).

Receive Floor Granted message (R: Floor Granted to other) (1610) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID, the floor participant:

may provide a floor taken notification to the MCPTT user;

shall start timer T13 (No RTP Media); and,

shall enter ‘O: has no permission’ state (1611).

Receive Floor Request message (R: Floor request) (1623) will bedescribed below.

Upon receiving Floor Request message, the floor participant:

shall start timer T40 (request buffer);

shall increment the counter C40 by 1;

shall buffer the received request; and

shall remain in ‘O: silence’ state (1615).

Timer T40 (request buffer) expires AND counter C40<2 (1623) will bedescribed below.

Upon expiry of timer T40 while number of received Floor Request messagesis less than 2, the floor participant:

shall reset the counter C40;

shall discard the buffered Floor Request messages; and,

shall remain in ‘O: silence’ state (1615).

Timer T40 (request buffer) expires AND counter C40>1 (1607) will bedescribed below.

Upon expiry of timer T40 while number of received Floor Request messagesis more than 1, the floor participant:

shall reset the counter C40;

shall start timer T41 (back-off) with a random value between [a, b];and,

shall enter ‘O: contention’ state (1606).

State: ‘O: has no permission’ (1611) will be described below.

In this state another floor participant does not have permission to sendmedia.

Sending Floor Request message (PTT button pressed) (1601) will bedescribed below.

If the floor participant receives an indication from the user that theuser wants to send media, the floor participant:

shall send the Floor Request message to other clients. The Floor Requestmessage shall be populated as follows:

shall start the timer T11 (Request re-send); and

shall enter ‘O: pending request’ state (1604).

Receive Floor Release message (R: Floor Release) (1617) will bedescribed below.

When a Floor Release message is received and if the SSRC in the FloorRelease message matches the SSRC in the last RTP media packet received,the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall stop timer T13 (No RTP Media);

shall enter ‘O: silence’ state (1615); and

may provide floor idle notification to the MCPTT user.

T13 (No RTP Media) timer fired (1617) will be described below.

On firing of T13 (No RTP Media) timer, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall enter ‘O: silence’ state (1615); and

may provide floor idle notification to the MCPTT user.

Receiving Floor Granted message (R: Floor Granted) (1609) will bedescribed below.

When a Floor Granted message is received and if the User ID in the FloorGranted message doesn't match its own User ID, the floor participant:

shall remain in the ‘O: has no permission’ state (1611).

Receiving Floor Deny message (R: Floor Granted)

When a Floor Deny message is received (i.e. after sending a FloorRequest in this state),

the floor control client:

shall stay in the state ‘O: has no permission’ (1611).

Receiving RTP media (R: RTP media) (1609) will be described below.

Upon receiving RTP media packets, the floor participant:

shall request the MCPTT client to render the received RTP media packets;

shall restart timer T30 (During silence);

shall restart timer T13 (No RTP Media); and

shall remain in ‘O: has no permission’ state (1611).

State: ‘O: has permission’ (1635) will be described below.

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

Send RTP Media packets (S: RTP Media) (1637) will be described below.

Upon receiving encoded media from the user or if encoded media isalready buffered the floor participant:

shall request the MCPTT client to start sending RTP media packetstowards other MCPTT clients;

shall restart timer T30 (During silence); and

shall remain in the current state.

Receive Floor Release message (R: Floor Release) (1637) will bedescribed below.

Upon receiving a Floor Release message, the floor participant:

shall remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and

shall remain in ‘O: has permission’ state (1635).

Receive Floor Request (R: Floor Request) (1637) will be described below.

When a Floor Request message is received in a session where queuing modeis not used, the floor participant:

shall send the Floor Deny message including reason field toward theother floor participants; and

shall remain in ‘O: has permission’ state (1635).

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher, thefloor participant:

shall store the received Floor Request messages,

shall send the Floor Request Queue Status message. The Floor RequestQueue Status message shall be populated as follows:

should indicate the User ID of the MCPTT client in the floor requestqueue;

should indicate the SSRC of the MCPTT client in the floor request queue;

should indicate the position of the MCPTT client in the floor requestqueue; and

should indicate the priority level of the MCPTT client in the in thefloor request queue and

shall remain in ‘O: has permission’ state (1635).

Send Floor Release message (PTT button released with no pending requestin queue) (1627) will be described below.

Upon receiving an indication from the MCPTT user to release permissionto send RTP media, the floor participant:

shall send a Floor Release message towards other floor participants, ifno queued requests exist: The Floor Release message shall be populatedas follows:

shall start timer T30 (During silence); and

shall enter ‘O: silence’ state (1615).

Send Floor Granted message (PTT button released with pending request(s)in queue) (1636) will be described below.

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession), the floor participant:

shall request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

shall send the Floor Granted message toward the other floorparticipants. The Floor Granted message shall be populated as follows:

should indicate the User IDs of the MCPTT clients in the floor requestqueue;

should include the SSRCs of the floor participants in the floor requestqueue;

should include the positions of the floor participants in the floorrequest queue; and

should include the priority levels of the floor participants in the inthe floor request queue;

shall start timer T20 (Granted re-send);

shall start timer T30 (During silence); and

shall enter the ‘O: pending granted’ state (1628).

Receive Floor Request with pre-emption indication (R: Floor Request withpre-emption) (1636) will be described below.

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

shall request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

shall send a Floor Granted message;

shall start timer T20 (Granted re-send);

if floor control queuing mode is used in the session, the Floor Grantedmessage shall be populated as follows:

should include User IDs of the floor participants in the floor requestqueue;

should include SSRCs of the floor participants in the floor requestqueue;

should include queue positions of the floor participants in the floorrequest queue; and

should include the priority levels of the floor participants in the inthe floor request queue;

shall start timer T30 (During silence); and

shall enter the ‘O: pending granted’ state (1628).

State: ‘O: pending request’ (1604) will be described below.

In this state the MCPTT client is waiting for a response to a Floorrequest message.

Receive RTP media (R: RTP media) (1602) will be described below.

Upon receiving RTP media packets, the floor participant:

shall request the MCPTT client to render the RTP media packets;

shall reset the counter associated with T11 (request re-send);

shall restart timer T30 (During silence);

shall restart (or start, if not running already) the timer T13 (No RTPmedia); and

shall remain in ‘O: pending request’ state (1604).

Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1619) will be described below.

Upon receiving Floor Request Queue Status message, the floorparticipant:

shall update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

shall stop the timer T11 (Request re-send); and

shall enter ‘O: queued’ state (1630).

Receive Floor Deny message (R: Floor Deny) (1603) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

shall stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

shall enter ‘O: has no permission’ state (1611).

Send Floor Release message (PTT button released) (1613) will bedescribed below.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

shall send a Floor Release message towards other floor participants;

shall stop the timer T11 (request re-send): and

shall enter ‘O: silence’ state (1615).

Send Floor Taken message (Timer T11 fired N times) (1626) will bedescribed below.

On the N^(th) firing of timer T11 (request re-send), the floorparticipant:

shall send Floor Taken message towards other floor participants;

shall stop timer T13 (no RTP media), if running;

shall stop timer T30 (During silence), if running; and

shall enter ‘O: has permission’ state (1635).

Receive Floor Granted message (R: Floor Granted to me) (1626) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall stop timer T13 (No RTP Media), if running;

shall stop the timer T11 (request re-send);

shall stop timer T30 (During silence), if running; and

shall enter ‘O: has permission’ state (1635).

Receive Floor Granted message (R: Floor Granted to other) (1602) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall reset the counter associated with T11 (request re-send); and

shall remain in ‘O: pending request’ state (1604).

T11 (Request re-send) timer fired (T11 timer fired) (1602) will bedescribed below.

On firing of timer T11 (Request re-send), the floor participant:

shall send the Floor Request message to other floor participants;

shall restart the timer T11 (Request re-send); and

shall remain in the ‘O: pending request’ state (1604).

Receive Floor Taken message (R: Floor Taken) (1602) will be describedbelow.

Upon receiving Floor Taken message, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets, if rendering;

shall reset the counter associated with T11 (request re-send);

shall remain in ‘O: pending request’ state (1604).

Receive Floor Request message (R: Floor request)

Upon receiving Floor Request message, if the priority of request ishigher than priority of the floor participant or if the SSRC of requestis higher than SSRC of the floor participant with same priority, thefloor participant:

shall reset the counter associated with T11 (request re-send); and

shall remain in ‘O: pending request’ state (1604).

State: ‘O: pending granted’ (1628) will be described below.

In this state the MCPTT client is waiting for another client to takeover the role of floor controller.

The Timer T20 (Granted re-send) is running in this state.

Receive RTP Media (R: RTP Media) (1625) will be described below.

Upon receiving the RTP media, the floor participant:

shall request the MCPTT client to render the received RTP media packets;

shall stop timer T20 (Granted re-send), if running;

shall stop timer T33 (Pending user action), if running;

shall restart timer T30 (During silence);

shall start timer T13 (no RTP media); and

shall enter ‘O: has no permission’ state (1611).

T20 (Granted re-send) timer fired (T20 timer fired) (1632) will bedescribed below.

On firing of timer T20 (Granted re-send), the floor participant:

shall send again the Floor Granted message toward the other floorparticipants. The Floor Granted message shall be populated as follows:

should indicate the list of User IDs of the MCPTT clients in the floorrequest queue;

should indicate the list of SSRCs of the MCPTT clients in the floorrequest queue;

should indicate the list of positions of the MCPTT clients in the floorrequest queue; and

should indicate the list of priority levels of the MCPTT clients in thein the floor request queue;

shall restart the timer T20 (Granted re-send); and

shall remain in ‘O: pending granted’ state (1628).

T20 (Granted re-send) timer fired N times (1632) will be describedbelow.

On the N^(th) firing of timer T20 (Granted re-send) with more request(s)pending in the queue, the floor participant:

shall reset the count of N; 2 shall start the timer T33 (Pending useraction); and

shall remain in ‘O: pending granted’ state (1628).

T33 (Pending user action) timer fired (T33 timer fired) (1624) will bedescribed below.

On firing of timer T33 (Pending user action), the floor participant:

shall send a Floor Release message towards other floor participants;and,

shall enter ‘O: silence’ state (1615).

PTT button pressed (1632) will be described below.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may notify the MCPTT user about rejection; and,

shall remain in ‘O: pending granted’ state (1628).

Receive Floor Release message (R: Floor Release) (1632) will bedescribed below.

Upon receiving a Floor Release message, the floor participant:

shall remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and

shall remain in ‘O: pending granted’ state (1628).

Receive Floor Request (R: Floor Request) (1632) will be described below.

When a Floor Request message is received, the floor participant:

shall send the Floor Deny message including reason field toward theother floor participants; and

shall remain in ‘O: pending granted’ state (1628).

State: ‘O: queued (1630) will be described below.

In this state the MCPTT client is waiting for a response to a pendingrequest.

Receive RTP media (R: RTP media) (1633) will be described below.

Upon receiving RTP media packets, the floor participant:

shall request the MCPTT client to render the RTP media packets;

shall restart timer T30 (During silence);

shall restart timer T13 (no RTP media); and

shall remain in ‘O: queued’ state (1630).

Receive Floor Request Queue Status message (R: Floor Request QueueStatus) (1633) will be described below.

Upon receiving Floor Request Queue Status message, the floorparticipant:

shall update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position; and

shall remain in ‘O: queued’ state (1630).

Receive Floor Deny message (R: Floor Deny) (1629) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

shall stop the timer T33 (Pending user action), if running; and

shall enter ‘O: has no permission’ state (1611).

User indication for release of pending request (1629) will be describedbelow.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

shall send a Floor Release message towards other floor participants;

shall stop the timer T33 (Pending user action), if running; and

shall enter ‘O: has no permission’ state (1611).

Receiving Floor Granted message (R: Floor Granted to me) (1633) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall start timer T33 (Pending user action);

may notify the MCPTT user about waiting user indication sending RTPmedia; and

shall remain in ‘O: queued’ state (1630).

T33 (Pending user action) timer fired with request pending in queue(1629) will be described below.

shall enter ‘O: has no permission’ state (1611).

T33 (Pending user action) timer fired with no request pending in queue(1622) will be described below.

shall enter ‘O: silence’ state (1615).

User indication for accept of pending request (1634) will be describedbelow.

If the floor participant receives an indication from the user that theuser wants to send media and the timer T33 (Pending user action) isrunning, the floor participant:

shall stop the timer T33 (Pending user action);

shall stop timer T30 (During silence), if running; and

shall enter ‘O: has permission’ state (1635).

Receive Floor Granted message (R: Floor Granted to other) (1633) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets; and,

shall remain in ‘O: queued’ state (1630).

T13 (No RTP Media) timer fired (1620) will be described below.

On firing of T13 (No RTP Media) timer, the floor participant:

shall request the MCPTT client to stop rendering received RTP mediapackets;

shall send the Floor Request message to other floor participants,

shall start the timer T11 (Request re-send); and

shall enter ‘O: pending request’ state (1604).

State: ‘O: contention’ (1606) will be described below.

In this state the MCPTT client is trying to resolve race conditionbetween multiple simultaneous floor requests which were buffered in ‘O:silence’ state.

The MCPTT client chooses the Floor Request with highest priority orhighest value in ‘SSRC’ field if the priority is same and generates theFloor Granted message. A random back-off mechanism is in place so thatonly a single MCPTT client sends the Floor Granted message.

Timer T41 is running in this state.

Receive Floor Granted message to other (R: Floor Granted)

Upon receiving a Floor Grant message, the MCPTT client:

shall stop timer T41 (back-off); and

shall enter ‘O: has no permission’ state (1611).

Timer Ty (back-off) expires

Upon expiry of timer T41 (back-off), the MCPTT client:

shall send the Floor Granted message toward the other floorparticipants.

shall enter ‘O: has no permission’ state (1611).

State: Any state (1612) will be described below.

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’ state(1621) and the ‘Releasing’ state.

Receive MCPTT call release (R: MCPTT call release) (1614) will bedescribed below.

Upon receiving an MCPTT call release request from the application andsignaling plane when the MCPTT call is going to be released or firing oftimer T30 (During silence), the floor participant:

shall stop sending floor control messages towards other floorparticipants;

shall request the MCPTT client to stop sending and receiving RTP mediapackets;

shall release all resources including any running timers associated withthe MCPTT call;

shall terminate the instance of floor participant state transitiondiagram; and

shall enter ‘Start-stop’ state (1621).

A Floor participant state diagram with resolving collision of multiplearbitrators is disclosed.

The floor participant may behave according to the state diagram and thefollowing transitions. The received floor messages and the RTP mediapackets are inputs to the state machine according to their arrivalorder. They are not ignored unless otherwise stated. The MCPTT clientalso provides input to the state machine as request to talk (press PTTbutton) or as end of talk (release PTT button).

FIG. 17 show the ‘Floor participant state diagram —basic operation’ toresolve collision of multiple arbitrator

Referring to FIG. 17, if an RTP media packet or a floor control messagearrives in a state where there is no specific procedure specified forthe RTP media packet or the received floor control message, the floorparticipant shall discard the floor control message or the RTP mediapacket and shall remain in the current state. A badly formatted RTPpacket or floor control message received in any state is ignored by thefloor participant and does not cause any change of the current state.

An operation in the state “Start-stop” 1719 is described.

When a new instance of the state machine is created, before any floorcontrol related input is applied, the state machine is in the‘Start-stop’ state 1719. Similarly, when the call is released the statemachine shall return to the ‘Start-Stop’ state 1719.

In the state “Start-stop” 1719, the MCPTT call may be established by anoriginating MCPTT user.

When an MCPTT call is established with session announcement including anexplicit floor request in the state “Start-stop” 1719, in operation1725, the originating floor participant may create an instance of afloor participant state transition diagram for basic operation statemachine, and send Floor Granted message towards other floor participantsThe Floor Granted message may indicate the own User ID in the message.And the originating floor participant may start timer T30 (Duringsilence), and enter ‘O: has permission’ state 1730.

In the state “Start-stop” 1719, the MCPTT call may be established by aterminating MCPTT user.

When an MCPTT call is established in the state “Start-stop” 1719, inoperation 1715, the terminating floor participant may create an instanceof a floor participant state transition diagram for basic operationstate machine, start timer T30 (During silence), and enter ‘O: silence’state 1712.

An operation in the state: ‘O: silence’ 1712 is described.

In this state a none of the MCPTT clients in the session is acting as afloor control server.

If the floor participant receives an indication from the MCPTT user tosend media in the state: ‘O: silence’ 1712, in operation 1705, the floorparticipant may send the Floor Request message (PTT button pressed) toother floor participants, start the timer T11 (Request re-send), andenter ‘O: pending request’ state.

Upon receiving RTP media packets and if there is no stored SSRC of thecurrent arbitrator (R: RTP media) in the state: ‘O: silence’ 1712, inoperation 1709, the floor participant may provide a floor takennotification to the MCPTT user, restart timer T30 (During silence), setthe stored SSRC of the current arbitrator to the SSRC of RTP mediapacket, restart (or start, if not running already) timer T13 (No RTPMedia), request the MCPTT client to start rendering received RTP mediapackets, and enter ‘O: has no permission’ state 1710.

Otherwise, if SSRC of floor participant sending the media matches thestored SSRC of current arbitrator in the state: ‘O: silence’ 1712, inoperation 1709, the floor participant may restart (or start, if notrunning already) timer T13 (No RTP Media), restart timer T30 (Duringsilence), request the MCPTT client to start rendering received RTP mediapackets, and enter ‘O: has no permission’ state 1710.

When a Floor Granted message is received and if the User ID in the FloorGranted message does not match its own User ID (R: Floor Granted toother) in the state: ‘O: silence’ 1712, in operation 1709, the floorparticipant may provide a floor taken notification to the MCPTT user,set the stored SSRC of the current arbitrator to the SSRC of user towhom the floor was granted in the Floor Granted message, start timer T13(No RTP Media), and enter ‘O: has no permission’ state 1710.

An operation in the state: ‘O: has no permission’ 1710 is described.

In this state another floor participant does not have permission to sendmedia.

If the floor participant receives an indication from the user that theuser wants to send media (PTT button pressed) in the state: ‘O: has nopermission’ 1710, in operation 1701, the floor participant may send theFloor Request message to other clients. The Floor Request message may bepopulated by starting the timer T11 (Request re-send), and entering ‘O:pending request’ state 1703.

When a Floor Release message is received and if the SSRC in the FloorRelease message matches the SSRC in the last RTP media packet received(R: Floor Release) in the state: ‘O: has no permission’ 1710, inoperation 1709, the floor participant may request the MCPTT client tostop rendering received RTP media packets, stop timer T13 (No RTPMedia), clear the stored SSRC of the current arbitrator, enter ‘O:silence’ state 1712, and provide floor idle notification to the MCPTTuser.

On expiry of T13 (No RTP Media) timer in the state: ‘O: has nopermission’ 1710, in operation 1709, the floor participant may requestthe MCPTT client to stop rendering received RTP media packets, clear thestored SSRC of the current arbitrator, enter ‘O: silence’ state 1712,and provide floor idle notification to the MCPTT user.

When a Floor Granted message is received and if the User ID in the FloorGranted message does not match its own User ID and SSRC of floorparticipant sending the Floor Granted message matches the stored SSRC ofcurrent arbitrator (R: Floor Granted to other) in the state: ‘O: has nopermission’ 1710, in operation 1706, the floor participant may requestthe MCPTT client to stop rendering received RTP media packets, and setthe stored SSRC of the current arbitrator to the SSRC of user to whomthe floor was granted in the Floor Granted message, and remain in the‘O: has no permission’ state 1710.

Upon receiving RTP media packets (R: RTP media) in the state: ‘O: has nopermission’ 1710, in operation 1706, the floor participant may requestthe MCPTT client to render the received RTP media packets, restart timerT30 (During silence), restart timer T13 (No RTP Media), and remain in‘O: has no permission’ state 1710.

An operation in the state: ‘O: has permission’ 1730 is described.

In this state the MCPTT client is acting as a floor control server andhas the permission to send media.

Upon receiving encoded media from the user or if encoded media isalready buffered (S: RTP Media) in the state: ‘O: has permission’ 1730,in operation 1731, the floor participant may request the MCPTT client tostart sending RTP media packets towards other MCPTT clients, and remainin ‘O: has permission’ state 1730.

Upon receiving a Floor Release message (R: Floor Release) in the state:‘O: has permission’ 1730, in operation 1731, the floor participant mayremove the sender of the Floor Release message from the queue, if theUser ID in the floor release message matches the queued request of UserID, and remain in ‘O: has permission’ state 1730.

When a Floor Request message is received in a session where queuing modeis not used (R: Floor Request) in the state: ‘O: has permission’ 1730,in operation 1731, the floor participant may send the Floor Deny messageincluding reason field toward the other floor participants, and remainin ‘O: has permission’ state 1730.

When a Floor Request message is received in a session where queuing modeis used and if the priority level of the message is not higher (R: FloorRequest) in the state: ‘O: has permission’ 1730, in operation 1731, thefloor participant may store the received Floor Request messages, andsend the Floor Queue Position Info message. The Floor Queue PositionInfo message may be populated by indicating the User ID of the MCPTTclient in the floor request queue, indicating the SSRC of the MCPTTclient in the floor request queue, indicating the position of the MCPTTclient in the floor request queue, and indicating the priority level ofthe MCPTT client in the in the floor request queue. And the floorparticipant may remain in ‘O: has permission’ state 1730.

Upon receiving an indication from the MCPTT user to release permissionto send RTP media in the state: ‘O: has permission’ 1730, the floorparticipant may send a Floor Release message towards other floorparticipants (PTT button released with no pending request in queue), ifno queued requests exist. The Floor Release message shall be populatedas follows by starting timer T30 (During silence), clearing the storedSSRC of the current arbitrator, and entering ‘O: silence’ state 1712.

When no more encoded media is received from the user and if at least oneFloor Request message is stored (i.e. queuing mode is used in thesession) in the state: ‘O: has permission’ 1730, in operation 1729, thefloor participant may request the MCPTT client to stop sending RTP mediapackets towards other MCPTT clients, and send the Floor Granted messagetoward the other floor participants (PTT button released with pendingrequest(s) in queue). The Floor Granted message shall be populated byindicating the User IDs of the MCPTT clients in the floor request queue,including the SSRCs of the floor participants in the floor requestqueue, including the positions of the floor participants in the floorrequest queue, and including the priority levels of the floorparticipants in the in the floor request queue.

And the floor participant may set the stored SSRC of the currentarbitrator to the SSRC of user to whom the floor was granted in theFloor Granted message, start timer T20 (Granted re-send), start timerT30 (During silence), and enter the ‘O: pending granted’ state 1723.

Receive Floor Request with pre-emption indication (R: Floor Request withpre-emption) (1729) will be described below.

When a Floor Request message is received with a pre-emption priorityhigher than priority of the floor participant, the floor participant:

may request the MCPTT client to stop sending RTP media packets towardsother MCPTT clients;

may send a Floor Granted message;

may start timer T20 (Granted re-send);

if floor control queuing mode is used in the session, the Floor Grantedmessage may be populated as follows:

may include User IDs of the floor participants in the floor requestqueue;

may include SSRCs of the floor participants in the floor request queue;

may include queue positions of the floor participants in the floorrequest queue; and

may include the priority levels of the floor participants in the in thefloor request queue;

may a start timer T30 (During silence); and

may enter the ‘O: pending granted’ state (1723).

State: ‘O: pending request’ (1703) will be described below.

In this state, the MCPTT client is waiting for a response to a Floorrequest message.

In this state, a timer T11 (request re-send) is running.

To resolve a race condition between multiple simultaneous floorrequests, the MCPTT client resets the counter associated with T1, ifanother floor request with higher priority or higher SSRC, in case thepriority is same, is received.

Receive RTP media (R: RTP media) (1717) will be described below.

Upon receiving RTP media packets and if there is no stored SSRC of thecurrent arbitrator, the floor participant:

may request the MCPTT client to render the RTP media packets;

may reset the counter associated with T11 (request re-send);

may restart timer T30 (During silence);

may set the stored SSRC of the current arbitrator to the SSRC of RTPmedia packet;

may restart (or start, if not running already) the timer T13 (No RTPmedia); and

may remain in ‘O: pending request’ state (1703).

Otherwise, if SSRC of floor participant sending the media matches thestored SSRC of current arbitrator, the floor participant:

may request the MCPTT client to render the RTP media packets;

may reset the counter associated with T11 (request re-send);

may restart timer T30 (During silence);

may restart (or start, if not running already) the timer T13 (No RTPmedia); and

may remain in ‘O: pending request’ state (1703).

Receive Floor Queue Position Info message (R: Floor Queue Position Info)will be described below.

Upon receiving Floor Request Queue Status message, the floorparticipant:

may update the queue status, if the User ID in the Floor Request QueueStatus message matches its own User ID;

may notify the MCPTT user about the queue position;

may stop the timer T11 (Request re-send); and

may enter ‘O: queued’ state (1724).

Receive Floor Deny message (R: Floor Deny) (1704) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

may stop the timer T11 (Request re-send), if the User ID in the FloorDeny message matches its own User ID; and,

may enter ‘O: has no permission’ state (1710).

Send Floor Release message (PTT button released) (1708) will bedescribed below.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants;

may stop the timer T11 (request re-send);

may clear the stored SSRC of the current arbitrator; and

may enter ‘O: silence’ state (1712).

Send Floor Granted to me message (Timer T11 expired N times) (1721) willbe described below.

On the N^(th) expiry of timer T11 (request re-send), the floorparticipant:

may send the Floor Granted message toward the other floor participants.The Floor Granted message may be populated as follows:

may indicate the own User ID in the message

may stop timer T13 (no RTP media), if running;

may stop timer T30 (During silence), if running; and

may enter ‘O: has permission’ state (1730).

Receive Floor Granted message (R: Floor Granted to me) (1721) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID and SSRC of floor participantsending the Floor Granted message matches the stored SSRC of currentarbitrator, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may stop timer T13 (No RTP Media), if running;

may stop the timer T11 (request re-send);

may stop timer T30 (During silence), if running; and

may enter ‘O: has permission’ state (1730).

Receive Floor Granted message (R: Floor Granted to other) (1706) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID and SSRC of floorparticipant sending the Floor Granted message matches the stored SSRC ofcurrent arbitrator, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may set the stored SSRC of the current arbitrator to the SSRC of user towhom the floor was granted in the Floor Granted message;

may reset the counter associated with T11 (request re-send);

may re-start timer T11 (request re-send); and

may remain in ‘O: pending request’ state (1703).

T11 (Request re-send) timer expired (T11 timer expired) (1702) will bedescribed below.

On expiry of timer T11 (Request re-send), the floor participant:

may send the Floor Request message to other floor participants;

may restart the timer T11 (Request re-send); and

may remain in the ‘O: pending request’ state (1703).

Receive Floor Request message (R: Floor request) (1702) will bedescribed below.

Upon receiving Floor Request message, if the priority of receivedrequest is higher than priority of the floor participant or if the SSRCof received request is higher, if the priority is same, the floorparticipant:

may reset the counter associated with T1 (request re-send);

may re-start timer T11 (request re-send); and

may remain in ‘O: pending request’ state (1703).

State: ‘O: pending granted’ (1723) will be described below.

In this state the MCPTT client is waiting for another client to takeover the role of floor controller.

The Timer T20 (Granted re-send) is running in this state.

Receive RTP Media (R: RTP Media) (1717) will be described below.

Upon receiving the RTP media and the SSRC of RTP media packet matcheswith the stored SSRC of current arbitrator, the floor participant:

may request the MCPTT client to render the received RTP media packets;

may stop timer T20 (Granted re-send), if running;

may stop timer T33 (Pending user action), if running;

may restart timer T30 (During silence);

may start timer T13 (no RTP media); and

may enter ‘O: has no permission’ state (1710).

T20 (Granted re-send) timer expired (T20 timer expired) (1726) will bedescribed below.

On expiry of timer T20 (Granted re-send), the floor participant:

may send again the Floor Granted message toward the other floorparticipants. The Floor Granted message may be populated as follows:

may indicate the list of User IDs of the MCPTT clients in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients in the floor requestqueue;

may indicate the list of positions of the MCPTT clients in the floorrequest queue; and

may indicate the list of priority levels of the MCPTT clients in the inthe floor request queue;

may restart the timer T20 (Granted re-send); and

may remain in ‘O: pending granted’ state (1723).

T20 (Granted re-send) timer expired N times (with pending request(s) inthe queue (Timer T20 expired N times AND pending request(s) in queue)(1726) will be described below.

On the expiry of timer T20 (Granted re-send) for a configurable numberof times with request pending in the queue, the floor participant:

may reset the count of N;

may start the timer T33 (Pending user action); and

may remain in ‘O: pending granted’ state (1723).

T20 (Granted re-send) timer expired N times with no pending request inthe queue (Timer T20 expired N times AND no pending request in queue)(1716) will be described below.

On the expiry of timer T20 (Granted re-send) for a configurable numberof times with no request pending in the queue, the floor participant:

may reset the count of N;

may clear the stored SSRC of the current arbitrator; and

may enter ‘O: silence’ state (1712).

T33 (Pending user action) timer expires with no pending request in thequeue (T33 timer expires AND no pending request in queue) (1716) will bedescribed below.

On expiry of timer T33 (Pending user action) with no request pending inthe queue, the floor participant:

may send a Floor Release message towards other floor participants;

may clear the stored SSRC of the current arbitrator; and

may enter ‘O: silence’ state (1712).

T33 (Pending user action) timer expires with pending request(s) in thequeue (T33 timer expired AND pending request(s) in queue) (1726) will bedescribed below.

On the expiry of timer T33 (Pending user action) with more request(s)pending in the queue, the floor participant:

may send the Floor Granted message for the next pending request in thequeue towards other floor participants. The Floor Granted message may bepopulated as follows:

may indicate the list of User IDs of the MCPTT clients next in the floorrequest queue;

may indicate the list of SSRCs of the MCPTT clients next in the floorrequest queue;

may indicate the list of positions of the MCPTT clients next in thefloor request queue; and

may indicate the list of priority levels of the MCPTT clients next inthe in the floor request queue;

may set the stored SSRC of the current arbitrator to the SSRC of user towhom the floor was granted in the Floor Granted message;

may start the timer T20 (Granted re-send); and

may remain in ‘O: pending granted’ state (1723).

PTT button pressed (1701) will be described below.

If the floor participant receives an indication from the MCPTT user tosend media, the floor participant:

may notify the MCPTT user about rejection; and,

may remain in ‘O: pending granted’ state (1723).

Receive Floor Release message (R: Floor Release) (1726) will bedescribed below.

Upon receiving a Floor Release message, the floor participant:

may remove the sender of the Floor Release message from the queue, ifthe User ID in the floor release message matches the queued request ofUser ID; and

may remain in ‘O: pending granted’ state (1723).

Receive Floor Request (R: Floor Request) (1726) will be described below.

When a Floor Request message is received, the floor participant:

may send the Floor Deny message including reason field toward the otherfloor participants; and

may remain in ‘O: pending granted’ state (1723).

State: ‘O: queued (1724) will be described below.

In this state the MCPTT client is waiting for a response to a pendingrequest.

Receive RTP media (R: RTP media) (1727) will be described below.

Upon receiving RTP media packets and the SSRC of RTP media packetmatches with the

stored SSRC of current arbitrator, the floor participant:

may request the MCPTT client to render the RTP media packets;

may restart timer T30 (During silence);

may restart timer T13 (no RTP media); and

may remain in ‘O: queued’ state (1724).

Receive Floor Queue Position Info message (R: Floor Queue Position Info)will be described below.

Upon receiving Floor Queue Position Info message, the floor participant:

may update the queue position, if the User ID in the Floor QueuePosition Info message matches its own User ID:

may notify the MCPTT user about the queue position; and

may remain in ‘O: queued’ state (1724).

Receive Floor Deny message (R: Floor Deny) (1732) will be describedbelow.

Upon receiving Floor Deny message, the floor participant:

may stop the timer T33 (Pending user action), if running; and

may enter ‘O: has no permission’ state (1710).

User indication for release of pending request (1728) will be describedbelow.

When an indication from the MCPTT user to release the pending requestfor the floor is received, the floor participant:

may send a Floor Release message towards other floor participants

may stop the timer T33 (Pending user action), if running; and

may enter ‘O: has no permission’ state (1710).

Receiving Floor Granted message (R: Floor Granted to me) (1727) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message matches its own User ID and SSRC of floor participantsending the Floor Granted message matches the stored SSRC of currentarbitrator, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may start timer T33 (Pending user action);

may notify the MCPTT user about of the floor grant; and

may remain in ‘O: queued’ state (1724).

T33 (Pending user action) timer expires (1720) will be described below.

may enter ‘O: silence’ state (1712).

User indication for accept of pending request (1728) will be describedbelow.

If the floor participant receives an indication from the user that theuser wants to send media and the timer T33 (Pending user action) isrunning, the floor participant:

may stop the timer T33 (Pending user action);

may stop timer T30 (During silence), if running; and

may enter ‘O: has permission’ state (1730).

Receive Floor Granted message (R: Floor Granted to other) (1727) will bedescribed below.

Upon receiving Floor Granted message and if the User ID in the FloorGranted message does not match its own User ID and SSRC of floorparticipant sending the Floor Granted message matches the stored SSRC ofcurrent arbitrator, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may set the stored SSRC of the current arbitrator to the SSRC of user towhom the floor was granted in the Floor Granted message; and

may remain in ‘O: queued’ state (1724).

T13 (No RTP Media) timer expires (1718) will be described below.

On expiry of T13 (No RTP Media) timer, the floor participant:

may request the MCPTT client to stop rendering received RTP mediapackets;

may send the Floor Request message to other floor participants;

may start the timer T11 (Request re-send);

may clear the stored SSRC of the current arbitrator; and

may enter ‘O: pending request’ state (1703).

State: Any state (1707) will be described below.

This subclause describes the actions to be taken in all states definedfor the basic state diagram with the exception of the ‘Start-stop’state.

Receive MCPTT call release or timer T30 (during silence) expired (R:MCPTT call release OR Timer T30 expired) (1711) will be described below.

Upon receiving an MCPTT call release request from the application andsignaling plane when the MCPTT call is going to be released or expiry oftimer T30 (During silence), the floor participant:

may stop sending floor control messages towards other floorparticipants;

may request the MCPTT client to stop sending and receiving RTP mediapackets;

may release all resources including any running timers associated withthe MCPTT call;

may terminate the instance of floor participant state transitiondiagram; and

may enter ‘Start-stop’ state (1719).

Next, floor control detail messages will be described below.

A format of a RTCP APP message according to an embodiment of the presentdisclosure will be described with reference to FIG. 18.

FIG. 18 schematically illustrates a format of a RTCP APP messageaccording to an embodiment of the present disclosure.

Referring to FIG. 18, a floor control protocol is based on the RTCPApplication Packets (RTCP: APP), as defined in IETF RFC 3550, but thefloor control messages do not conform to the rules for compound RTCPpackets or RTCP packet transmission.

Each floor control message may be one RTCP: APP packet. These RTCP: APPpackets may not be sent in compound RTCP packets, but more than onefloor control message may be sent in a single IP packet. The structureof each floor control message is defined below.

The definition of the fields in the RTCP APP packet is found in IETF RFC3550.

The RTCP APP message includes P, Length, Name, and Application-dependentdata.

Here, each of P, Length, Name, and Application-dependent data will bedescribed below.

(1) P

The padding bit P may be set to 0.

(2) Length

The length field in the RTCP header is the length of the packet in32-bit words, not counting the first 32-bit word in which the lengthfield resides.

NOTE 1: The length field can indicate message size longer than specifiedin this version of the protocol. This can be the case e.g. if message isof later version of this protocol.

(3) Name

The 4-byte ASCII string in the RTCP header may be used to define the setof floor control messages to be unique with respect to other APP packetsthat the application might receive.

For the floor control protocol specified in present document the ASCIIname string may be: MCPT.

NOTE 2: The ASCII name field value i.e. MCPT does not correspond to thefloor control protocol version.

(4) Application-Dependent Data

The use of application dependent data is specified in the subclausewhere the floor control message is specified. If the length of theapplication dependent data is not a multiple of 4 bytes, the applicationdependent data may be padded to a multiple of 4 bytes. The value of thepadding bytes may be set to zero. The floor control client may ignorethe value of the padding bytes.

Handling of unknown fields and messages will be described below.

When a message is received the floor control client may:

-   -   ignore the whole message, if the subtype is unknown;    -   ignore the unspecified fields in the message (e.g. specified in        future version of the floor control protocol) and    -   ignore the syntactically incorrect optional fields.

Floor control protocol specific fields will be described below.

This subclause describes fields specific for the floor control protocolspecified in the present specification.

The floor control messages can include the floor control protocolspecific fields and if included, the floor control specific fields arecontained in the application-dependent data of the floor controlmessage.

Each floor control protocol specific field consists of an 8-bit FieldID, an 8-bit octet count describing the length of the field value notincluding this two-octet header, and the field value.

Table 2 lists the available fields including the assigned Field ID.

TABLE 2 Floor control specific fields Field name Field ID Description —000-099 Used by RTCP UserID 100 MCPPTT user identity Queue 101 Waitinglist Priority-level 102 Priority value — 103-255 Reserved for future use

Table 2 includes UserID, Queue, and Priority-level. Each of UserID,Queue, and Priority-level will be described below.

(1) UserID

The UserID field may include the value 100 (decimal) indicating thatthis information field is used to indicate the MCPTT useridentification.

The Identity-length field may include the value indicating the length ofthis item except padding.

If the length of the identity is not a multiple of 4 bytes except first16-bit words, the identity value field may be padded to a multiple of 4bytes except first 16-bit words. The value of the padding bytes may beset to zero. The floor control client may ignore the value of thepadding bytes.

(2) Queue

The Queue field may include the value 101 (decimal) indicating that thisadditional information field is used to indicate the number of waitingclients as next talker in the MCPTT call.

The Queue-length field may include the value 2 indicating the length ofthis item.

(3) Priority-Level

The Priority-level field may have the value 102 (decimal).

The Priority-length field may have the value 2 indicating the length ofthis item.

The Priority value field may consist of 16 bit parameter giving adefined Media Burst request priority level.

The defined priority levels that can be included in a Floor Requestmessage are:

1 Normal priority.

2 High priority.

3 Pre-emptive priority.

All other values are reserved and may not be used.

A format of a Floor Request message according to an embodiment of thepresent disclosure will be described with reference to FIG. 19.

FIG. 19 schematically illustrates a format of a Floor Request messageaccording to an embodiment of the present disclosure.

Referring to FIG. 19, the Floor Request message is a request from afloor control client to get permission to send media.

The following bit pattern in the subtype field may be used for the FloorRequest message: 00000.

The Floor Request message includes SSRC, UserID, and Priority. Each ofSSRC, UserID, and Priority will be described below.

(1) SSRC

The SSRC field may carry the SSRC of the floor control client.

(2) UserID

The UserID field may carry the MCPTT User ID of the floor controlclient.

(3) Priority

The priority-level may be included if between the floor control clientshave agreed to support queuing of floor requests.

The floor control client may include the Priority-level field if theMCPTT user has indicated that the floor request is desired at a levelother than normal priority, or if the floor control client wishes tochange the Priority-level of a queued floor request.

The coding of the floor request priority is specified in subclause4.1.2.4.

A format of a Floor Granted message according to an embodiment of thepresent disclosure will be described with reference to FIG. 20.

FIG. 20 schematically illustrates a format of a Floor Granted messageaccording to an embodiment of the present disclosure.

Referring to FIG. 20, the Floor Granted message is an action from thefloor control client which have a permission to transmit media to informthe requesting floor control client that it has been granted thepermission to send media.

The following bit pattern in the subtype field may be used for the FloorGranted message: 00001.

The Floor Granted message includes SSRC, UserID, Queue, Priority, Queueposition, Padding, SSRC, and UserID. Each of SSRC, UserID, Queue,Priority, Queue position, Padding, SSRC, and UserID will be describedbelow.

(1) SSRC

The SSRC field may carry the SSRC of the floor control client sendingthe floor control granted message.

The SSRC field may carry the SSRC of the floor control client granted apermission to send.

(2) UserID

The UserID field may carry the MCPTT User ID of the floor control clientgranted the permission to send media.

(3) Queue

The size field is the numbers of waiting clients in the MCPTT call. TheQueue includes set of priority, queue position, padding, SSRC, anduserID.

(4) Priority

The priority level field is a 1 byte field which defines the prioritylevel that is currently held by floor control client granted thepermission to send the media.

The defined priority levels that can be included in a Floor Grantedmessage are:

-   -   1—normal priority    -   2—high priority    -   3—pre-emptive priority

The default value if the priority option was not negotiated at MCPTTcall setup may be 1.

All other values are reserved.

(5) Queue Position

The queue position field defines the number of floor control clients inthe Floor Request Queue Status message that are ahead of the floorcontrol client.

(6) Padding

The last 8 bits are padding bits and may be set to zero.

(7) SSRC

The SSRC field may carry the SSRC of the floor control client.

(8) UserID

The UserID field may carry the MCPTT User ID of the floor control clientheld by floor control client granted the permission to send the media.

NOTE: The Priority, Queue position, Padding, UserID are a set indicatingthe floor control client waiting for receiving the Floor Grantedmessage. The set can be one or more floor control clients.

A format of a Floor Taken message according to an embodiment of thepresent disclosure will be described with reference to FIG. 21.

FIG. 21 schematically illustrates a format of a Floor Taken messageaccording to an embodiment of the present disclosure.

Referring to FIG. 21, the Floor Taken message is sent to informnon-requesting floor control client(s) that someone has been grantedpermission to send media.

The following bit pattern in the subtype field may be used for the FloorTaken message: 00010, when no acknowledgement reply is expected.

The Floor Taken message includes SSRC and UserID. Each of SSRC andUserID will be described below.

(1) SSRC

The SSRC field may carry the SSRC of the floor client granted apermission to send media.

(2) UserID

The UserID field may carry the MCPTT User ID of the floor controlclient.

A format of a Floor Deny message according to an embodiment of thepresent disclosure will be described with reference to FIG. 22.

FIG. 22 schematically illustrates a format of a Floor Deny messageaccording to an embodiment of the present disclosure.

Referring to FIG. 22, the Floor Deny message is sent as an action fromfloor control client granted the permission to send the media to therequesting floor control client to inform that the floor request wasrejected.

The following bit pattern in the subtype field may be used for the FloorDeny message: 00011.

Application-dependent data for the Floor Deny message includes a reasonin the reason code field and possibly followed by a text-string in thereason phrase field describing why the request was rejected. Therefore,the length of the packet will vary depending on the size of theapplication dependent field.

The Floor Deny message includes SSRC, UserID, and Reason code and reasonphrase.

Each of SSRC, UserID, and Reason code will be described below.

(1) SSRC

The SSRC field may carry the SSRC of the floor control client grantedthe permission to send the media.

(2) UserID

The UserID field may carry the MCPTT User ID of the floor control clientsending floor request message.

(3) Reason Code and Reason Phrase

The first 8 bits in the application-dependent data field is used for thereason code field.

The length field gives the length of the reason phrase field in bytes.If the length field is set to 0, there is no reason in the reason phrasefield. The reason phrase field can contain a text string with additionalinformation. The text string may use the same encoding as the textstrings in the SDES item CNAME as specified in IETF RFC 3550.

A format of a Floor Release message according to an embodiment of thepresent disclosure will be described with reference to FIG. 23.

FIG. 23 schematically illustrates a format of a Floor Release messageaccording to an embodiment of the present disclosure.

Referring to FIG. 23, the Floor Release message is sent as an actionfrom the floor control client sending floor request message to the floorcontrol client granted the permission to send the media to inform thatthe floor can be released.

The Floor Release message may also be sent if the floor control clienthas a request in the floor request queue. In this case, the FloorRelease message is sent to cancel the floor request in the queue iscancelled.

The following bit pattern in the subtype field may be used for the FloorRelease message: 00100.

The Floor Release message includes SSRC and UserID. Each of SSRC andUserID will be described below.

(1) SSRC

The SSRC field may carry the SSRC of the floor control client withpermission to send media.

(2) UserID

The UserID field may carry the MCPTT User ID of the floor control clientsending floor request message or granted the permission to send themedia.

A format of a Floor Request Queue Status message according to anembodiment of the present disclosure will be described with reference toFIG. 24.

FIG. 24 schematically illustrates a format of a Floor Request QueueStatus message according to an embodiment of the present disclosure.

Referring to FIG. 24, the Floor Request Queue Status message is sent bythe client with permission to notify the floor control client of itsposition in the floor request queue. The message is sent in response toa Floor Request message if the request is queued or as the response tothe Floor Request Queue Status Request message. It can be sent at othertimes, e.g. if the floor control client is removed from the floorrequest queue or if the position or priority of the request is changed.

The following bit pattern in the subtype field may be used for the FloorRequest Queue Status message: 01001.

The Floor Request Queue Status message includes SSRC, UserID, Priority,Queue position, and Padding. Each of SSRC, UserID, Priority, Queueposition, and Padding will be described below.

(1) SSRC

The SSRC field may carry the SSRC of the client with permission to sendmedia

(2) UserID

The UserID field may carry the MCPTT User ID of the floor control clientsending Floor Request message.

(3) Priority

The priority level field is a 1 byte field which defines the prioritylevel that is currently held by floor control client granted thepermission to send the media.

The defined priority levels that can be included in a Floor Grantedmessage are:

-   -   1—normal priority    -   2—high priority    -   3—pre-emptive priority

The default value if the priority option was not negotiated at MCPTTcall setup may be 1.

All other values are reserved.

(4) Queue Position

The queue position field defines the number of floor control clients inthe Floor Request Queue Status message that are ahead of the floorcontrol client.

(5) Padding

The last 8 bits are padding bits and may be set to zero.

Meanwhile, Timers in the floor control participant will be describedwith reference to Table 3.

Table 3 recommends timer values, describes the reason for of startingthe timer, normal stop and the action on expiry.

Table 3: Floor participant timers

TABLE 3 Floor participant timers Timer Timer value Cause of start Normalstop On expiry T11 — When the floor The reception of a If the counter isless ‘Request participant sends a Floor Floor Granted than N, a newFloor re-send’ Request message message or a Request message is FloorDeny sent and counter is message or Floor increased by 1. Request QueueStatus message or when User release PTT button. T13 Value shouldReception of an RTP Reception of a When T13 expires ‘no RTP be greaterthan media packet. Floor Release the floor control media’ max waitingT13 is reset and started message and client concludes that time againevery time an RTP Floor Granted to the there is no floor (T33*max mediapacket is received. me arbitrator at present. size of queue) When thefloor When the floor participant enters ‘O: has participant enters nopermission’ (e.g. ‘O: has receiving Floor Granted permission’ (e.g.message for other and receiving Floor Floor Taken message) Grantedmessage) T20 — When the floor arbitrator The reception of If the counteris less ‘Granted grants the permission to an RTP Media than M, a newFloor re-send’ send media to a floor packet in ‘O: Granted message istimer participant, which was pending granted’ sent and counter isqueued. increased by 1. T20 is also started again when the floor controlserver sends a Floor Granted message upon T20 expiry. T30 Value shouldReception of an RTP Release of the The floor control ‘during be greaterthan media packet. call. entity is released. silence’ T13. T30 is resetand started When the floor again every time an RTP participant entersmedia packet is received. ‘O: has When the floor permission participantleaves ‘O: has permission’ T33 Value should Reception/Transmission Whena floor Assume the ‘Pending be greater than of floor granted messageparticipant in ‘O: participant is out of user action’ T20*M. for queuedrequest. queued’ state coverage or doesn't pushes PTT push PTT button.button. Grant to next in Reception of RTP queue if any, media in ‘O:otherwise assume pending granted’ silence. T41 — Reception of more than1 Reception of a Send a Floor Granted ‘back-off’ Floor Request messagesFloor Granted message to the during T40 message. selected client.Reception of Floor Granted message to other T40 — Receipt of FloorRequest — If the value of ‘Request message during silence associatedcounter is buffer’ greater than 1 enter ‘O: contention’ state.Otherwise, ignore.

Further, counters in the floor control participant (off-network) will bedescribed with reference to Table 4.

The table 4 enlists counters, their limits and the action on expiry.

TABLE 4 Floor participant counters: Counter Limit Associated timer Onexpiry C11 — T11 Assume there is no ‘Request floor arbitrator and sendre-send’ Floor Taken message C20 — T20 Start T33 (Pending user ‘Grantedaction) timer to wait for re-send’ response of client (i.e. RTP mediapackets) C40 Not applicable T40 Not applicable ‘Request buffer’

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention as defined bythe appended claims and their equivalents.

What is claimed:
 1. A method performed by a user equipment (UE), the method comprising: receiving, from an other UE included in a group call in which the UE is included, a first message for requesting permission for transmission; identifying that the permission for transmission is granted to the other UE in case that the UE does not transmit, to the other UE, a second message in response to the first message repeatedly transmitted, and the UE receives, from the other UE, a third message indicating that the permission for transmission is granted to the other UE; and receiving media data from the other UE.
 2. The method of claim 1, wherein the other UE transmitting the third message is in a state that a counter associated with transmission of the first message reaches a predetermined value.
 3. The method of claim 2, wherein the counter indicates an expiry number of a timer expired by the repeated transmission of the first message.
 4. The method of claim 1, further comprising: transmitting, to the other UE, a fourth message indicating rejection of the permission for transmission in response to the first message in case that the UE has the permission for transmission.
 5. The method of claim 4, further comprising: transmitting media data to the other UE after transmitting the fourth message.
 6. A user equipment (UE) comprising: a transceiver; and a controller configured to: receive, via the transceiver, from an other UE included in a group call in which the UE is included, a first message for requesting permission for transmission, identify that the permission for transmission is granted to the other UE in case that the UE does not transmit, via the transceiver, to the other UE, a second message in response to the first message repeatedly transmitted and the UE receives, via the transceiver, from the other UE, a third message indicating that the permission for transmission is granted to the other UE, and receive, via the transceiver, media data from the other UE.
 7. The UE of claim 6, wherein the controller is further configured to: receive, via the transceiver, the third message from the other UE in a state that a counter associated with transmission of the first message reaches a predetermined value.
 8. The UE of claim 7, wherein the counter indicates an expiry number of a timer expired by the repeated transmission of the first message.
 9. The UE of claim 6, wherein the controller is further configured to: transmit, via the transceiver, to the other UE, a fourth message indicating rejection of the permission for transmission in response to the first message in case that the UE has the permission for transmission.
 10. The UE of claim 9, wherein the controller is further configured to: transmit, via the transceiver, media data to the other UE after transmitting the fourth message. 